WO2003023421A1 - Capacitance measuring circuit, capacitance measuring instrument, and microphone device - Google Patents

Capacitance measuring circuit, capacitance measuring instrument, and microphone device Download PDF

Info

Publication number
WO2003023421A1
WO2003023421A1 PCT/JP2002/009138 JP0209138W WO03023421A1 WO 2003023421 A1 WO2003023421 A1 WO 2003023421A1 JP 0209138 W JP0209138 W JP 0209138W WO 03023421 A1 WO03023421 A1 WO 03023421A1
Authority
WO
WIPO (PCT)
Prior art keywords
capacitor
detection circuit
capacitance
impedance
capacitance detection
Prior art date
Application number
PCT/JP2002/009138
Other languages
French (fr)
Japanese (ja)
Inventor
Masami Yakabe
Naoki Ikeuchi
Original Assignee
Sumitomo Metal Industries, Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sumitomo Metal Industries, Ltd. filed Critical Sumitomo Metal Industries, Ltd.
Priority to US10/488,763 priority Critical patent/US7019540B2/en
Priority to KR1020047003329A priority patent/KR100715062B1/en
Priority to EP02767922A priority patent/EP1426773A4/en
Publication of WO2003023421A1 publication Critical patent/WO2003023421A1/en
Priority to NO20032012A priority patent/NO20032012L/en

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04RLOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R29/00Monitoring arrangements; Testing arrangements
    • H04R29/004Monitoring arrangements; Testing arrangements for microphones
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables

Definitions

  • Capacitance detection circuit Description Capacitance detection circuit, capacitance detection device, and microphone device
  • the present invention relates to a circuit and a device for detecting a capacitance, and more particularly to a circuit, a device and a microphone device for detecting a minute capacitance with high accuracy.
  • FIG. 1 is a circuit diagram showing this capacitance detection circuit.
  • a capacitance sensor 92 formed by the electrodes 90 and 91 is connected to an inverting input terminal of an operational amplifier 95 via a signal line 93.
  • the capacitor 96 is connected between the output terminal of the operational amplifier 95 and the inverting input terminal, and the AC voltage Vac is applied to the non-inverting input terminal.
  • the signal line 93 is covered with a shield line 94 and is electrically shielded from disturbance noise.
  • the shield wire 94 is connected to the non-inverting input terminal of the operational amplifier 95.
  • the output voltage Vd is taken out from the output terminal of the operational amplifier 95 via the transformer 97.
  • the inverting input terminal and the non-inverting input terminal of the operational amplifier 95 are in the state of image short, and the signal line 93 connected to the inverting input terminal and the shield line connected to the non-inverting input terminal 9 4 have almost the same potential as each other.
  • the signal line 93 is guarded by the shield line 94, that is, the stray capacitance between the two is canceled, and an output voltage Vd which is hardly influenced by the stray capacitance is obtained. That can be is there.
  • the tracking error in the operational amplifier 95 may cause a difference between the voltage at the inverting input terminal and the voltage at the non-inverting input terminal in the marginal short state.
  • the phase and amplitude shifts are delicate in nature, and the detection error increases.
  • a compact amplifier circuit that converts voice detected by a capacitive sensor such as a capacitor microphone into an electrical signal with high sensitivity and high fidelity is required.
  • the present invention has been made in view of such a situation, and is capable of accurately detecting a minute capacitance, and is lightweight.
  • a capacitance detection circuit includes a capacitance detection circuit that outputs a detection signal corresponding to the capacitance of a capacitor to be detected.
  • An impedance converter having a high input impedance and a low output impedance, a capacitive first impedance element, an operational amplifier, and applying an AC voltage to the operational amplifier.
  • An input terminal of the impedance converter has one end of the capacitor to be detected and one end of the first impedance element.
  • the first impedance element and the impedance converter are included in a negative feedback path of the operational amplifier, and the detection capacitor and the capacitance detection circuit are provided adjacent to each other. It is characterized by having.
  • the capacitance detection circuit is a capacitance detection circuit that outputs a detection signal corresponding to the capacitance of a capacitor to be detected, wherein the input impedance is high and the output impedance is low.
  • One end of the capacitor to be detected and one end of the first impedance element are connected to an input terminal of the impedance converter, and the first impedance element and the impedance converter are connected to a negative feedback path of the operational amplifier.
  • the detected capacitor, the first impedance element, and the impedance converter are provided close to each other. And features.
  • the capacitance detection circuit comprises a connected resistor and a capacitor (first impedance element) connected between the output terminal of the operational amplifier and the input terminal of the impedance converter.
  • the input terminal of the impedance converter Connected between potentials, the capacitance detection circuit and the capacitor to be detected are adjacent, or short and close so that the stray capacitance of the signal line does not exceed 10 times the maximum value of the capacitance of the connected element To be provided.
  • the predetermined potential refers to any one of a certain reference potential, a predetermined DC potential, a ground potential, and a floating state, and an optimum one is selected according to the embodiment.
  • a resistor as a second impedance connected between the AC voltage generator and the inverting input terminal of the operational amplifier may be provided.
  • the capacitor to be detected and the capacitance detection circuit must be connected to each other. Should be provided as close as possible to each other. Or, the capacitor to be detected, the first impedance element, and the impedance
  • near j means that the stray capacitance of the signal line is larger than the capacitance value of the capacitance of the capacitor to be detected or the capacitance value of the capacitive first impedance element. This means that the stray capacitance of the signal line does not exceed the one-digit value of the capacitance value of the connected element. It has been found that the capacitance detection circuit can prevent the detection sensitivity from significantly deteriorating, and this has been obtained empirically. The capacitance can be measured by measuring the capacitance without connecting the capacitor, the first impedance element, and the impedance converter to the signal line. The state Contact.
  • an inverting amplifier circuit for inverting a signal at a signal output terminal an adding circuit for adding an output signal of the impedance converter and an output signal of the inverting amplifier circuit, May be added.
  • a resistor may be connected in parallel with the capacitor (first impedance element).
  • the detected capacitor is a capacitive sensor that detects a physical quantity according to a change in capacitance, and the capacitance detecting circuit is formed on a printed circuit board or a silicon substrate. However, it is preferable that the capacitive sensor and the substrate are fixed, or that they are integrally formed.
  • a capacitor microphone is used as the capacitor to be detected, and the capacitance detection circuit is realized by an IC, and the capacitor microphone and the IC are used. May be integrated and housed in a single case (shielded box) as a microphone used for mobile phones and the like. At this time, the capacitor microphone and the IC are fixed at adjacent positions, and are connected by a conductive plate, a wiring pattern, a wire bonding, or the like.
  • FIG. 1 is a circuit diagram of a conventional capacitance detection circuit.
  • FIG. 2 is a circuit diagram of the capacitance detection circuit according to the first embodiment of the present invention.
  • FIGS. 3A to 3E show examples of impedance converters usable in the present invention.
  • FIG. 4 is a circuit diagram of a capacitance detection circuit according to the second embodiment of the present invention.
  • FIG. 5 is a diagram (a cross-sectional view of a microphone) showing an application example of the capacitance detection circuit of the present invention to an electronic device.
  • FIG. 6 is a schematic external view of the microphone shown in FIG. 4, in which (a) is a plan view, (b) is a front view, and (c) is a bottom view.
  • FIG. 7 is a cross-sectional view of another example of the microphone.
  • FIG. 8 is a schematic external view of the microphone shown in FIG. 6, in which (a) is a plan view and (b) is a front view.
  • FIG. 9 is a circuit diagram of a capacitance detection circuit according to another embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION
  • FIG. 2 is a circuit diagram of the capacitance detection circuit 10 according to the first embodiment of the present invention.
  • the capacitance detection circuit 10 has a capacitor 17 to be detected (here, a capacitor microphone, etc., which detects various physical quantities by using a change in the capacitance Cs). (Capacitive sensor) is connected.
  • the capacitance detection circuit 10 includes an AC voltage generator 11 for generating an AC voltage, a resistor (R1) 12, a resistor (R2) 13, a operational amplifier 14, and an impedance element (here, It consists of a capacitor (capacitor Cf) 15 and an impedance converter 16, and outputs a detection signal (voltage V out) corresponding to the capacitance of the capacitor 17 to be detected from the signal output terminal 20.
  • One end of the AC voltage generator 11 is connected to a predetermined potential (ground in this example), and a constant AC voltage (voltage Vin, angular frequency ⁇ ) is generated from the other end (output terminal).
  • a resistor (R 1) 12 is connected between the output terminal of the AC voltage generator 11 and the inverted input terminal of the operational amplifier 14.
  • Operational amplifier 14 has extremely high input impedance and open loop gain. This is a high voltage amplifier, in which the non-inverting input terminal is connected to a predetermined potential (ground in this example), and the non-inverting input terminal and the inverting input terminal are in the state of imagery short.
  • the capacitor 15, the impedance converter 16, and the resistor (R 2) 13 are connected between the negative feedback path of the operational amplifier 14, that is, between the output terminal and the inverting input terminal of the operational amplifier 14. They are connected in series in this order.
  • the impedance converter 16 is a voltage amplifier whose input impedance is extremely high, whose output impedance is extremely low, and whose voltage gain is A times.
  • the input terminal 21 of the impedance converter 16 is connected to the negative terminal of the detected capacitor 17 via a conductor such as a signal line or a wiring pattern on a printed circuit board.
  • the other end of the capacitor 17 to be detected is connected to a predetermined potential (ground in this example).
  • the output terminal of the operational amplifier 14 is connected to the output signal of the capacitance detection circuit 10, that is, the signal output terminal 20 for outputting the detection signal corresponding to the capacitance of the capacitor 17 to be detected. It has been.
  • each of the variables A indicated by A times or the like represents a real number other than zero (0).
  • connection between the capacitor 17 to be detected and the capacitance detection circuit 10 is possible in order to prevent unnecessary stray capacitance from being added as a detection error or from being mixed with disturbance noise. It is preferable to connect with the shortest conductor (cable, copper foil wiring pattern, connection terminal, etc.). In addition, if possible, cover the detected capacitor 17 and the capacitance detecting circuit 10 entirely with a grounded shield member, or provide a shield to enhance the shielding against disturbance noise. It is preferable to store it in a box.
  • V inZ R l -V2 / R2
  • V 2 -(R 2 / R 1)-V in (Equation 1)
  • V 1 (1 / A) ⁇ V 2 (Equation 2)
  • V out i ⁇ (1 / j ⁇ C f) + V 1
  • V 1 -(R2 R 1) ⁇ (Vin / A) (Equation 4)
  • V out -(1 + C s / C f)-(R 2 / R 1)-(V in / A) (Equation 5) Is obtained.
  • the voltage Vout of the detection signal output from the signal output terminal 20 of the capacitance detection circuit 10 depends on the capacitance Cs of the capacitor 17 to be detected. . Therefore, by performing various signal processing on the voltage Vout, the capacitance Cs can be specified. Further, as can be seen from the fact that this equation 5 does not include the angular frequency ⁇ , the voltage V out of the detection signal is equal to the frequency of the AC signal Vin from the AC voltage generator 11 and the frequency of the detected signal. It does not depend on changes in the capacitor frequency. As a result, the capacitance of the capacitor 17 to be detected can be detected without depending on the frequency of the AC voltage applied to the capacitor 17 to be detected. No) A capacitance detection circuit is realized. Therefore, for a capacitor 17 such as a condenser microphone whose capacitance value changes at a certain frequency (voice band), the capacitance value can be calculated directly from its voltage value without frequency correction of the detected signal. Can be specified.
  • the operational amplifier 14 that supplies current to the capacitor 15 and the capacitor 17 to be detected has a non-inverting input terminal having a predetermined value. Connected to the potential and fixed. Therefore, unlike the operational amplifier 95 in the conventional circuit shown in FIG. 1, the operational amplifier 14 supplies a stable current with little noise without depending on the frequency of the input AC signal. Since the voltage is supplied to the capacitor 15 and the capacitor 17 to be detected, the minute capacitance of the capacitor 17 to be detected can be detected.
  • the original capacitance of C s (capacitor to be detected: microphone in this embodiment) is 20 pF.
  • the stray capacitance of the signal line is 200 pF Beyond, the detection sensitivity deteriorated considerably. Further, when the above Cs was confirmed at several different capacitance values, the same tendency was obtained.
  • the capacitance C f and the detected capacitor C s which are the first impedance element, are both capacitance elements connected to the signal line in this circuit, and the calculation is the same as above for both elements. It is likely to have consequences.
  • the detected capacitor, the first impedance element, and the impedance converter should be connected so that the stray capacitance of the signal line does not exceed the value of the capacitance of the relevant Cs or Cf by one order of magnitude. It was found that good detection sensitivity could be obtained when the distances were close to each other.
  • FIG. 3 shows a specific circuit example of the impedance converter 16 in the capacitance detection circuit 10 shown in FIG.
  • FIG. 3A shows a voltage follower using the operational amplifier 100. Inversion of operational amplifier 100 The input terminal and the output terminal are short-circuited. By setting the non-inverting input terminal of the operational amplifier 100 as the input of the impedance converter 16 and the output terminal of the operational amplifier 100 as the output of the impedance converter 16, the input impedance is reduced.
  • the impedance converter 16 is extremely high and has a voltage gain A of 1.
  • FIG. 3B shows a non-inverting amplifier circuit using the operational amplifier 101.
  • a resistor (R10) 110 is connected between the inverting input terminal of the operational amplifier 101 and the ground, and a feedback resistor (resistance (R11)) is connected between the inverting input terminal and the output terminal of the operational amplifier 101. 3 3) is connected.
  • R10 resistor
  • R11 feedback resistor
  • FIGS. 3 (a) and 3 (b) shows a circuit in which a buffer having a CMOS structure is added to the input stage of the operational amplifier as shown in FIGS. 3 (a) and 3 (b).
  • an N-type MOSFET 34 and a P-type MOSFET 35 are connected in series between the positive and negative power supplies via resistors 112 and 113, and the output of the buffer is connected to the operational amplifier 100. (Or 101) input.
  • FIG. 3 (d) shows a circuit such as the buffer in the input stage of FIG. 3 (c).
  • an N-type MOS FET 34 and a P-type MOS FET 35 are connected in series between the positive and negative power supplies, and an output is made from a connection between the two MOS FETs.
  • Figure 3 (e) shows the operational amplifier with the non-inverting input of the operational amplifier 102 as the input to the impedance converter, and connecting one end of a resistor 114 to the inverting input terminal of the operational amplifier 102.
  • the output of 102 and the inverting input are connected via a resistor 115.
  • an impedance converter 16 having an extremely high input impedance can be obtained.
  • FIG. 4 is a circuit diagram of the capacitance detection circuit 30 according to the second embodiment.
  • This capacitance detection circuit 30 has a large size ⁇ a core section 31 corresponding to the capacitance detection circuit 10 shown in FIG. 2, and a signal output terminal 20 of the core section 31.
  • Inverting section 32 that inverts with signal voltage V01 as input, and signal voltage V03 at output terminal 23 of inverting section 32 and alternating current of core section 31 It comprises an adder 33 that adds the signal voltage V 02 at the output terminal 22 and outputs a detection signal of the voltage V04 to the output terminal 24.
  • the core unit 31 is the same circuit as the capacitance detection circuit 10 shown in FIG. Therefore, the voltage V01 of the signal output terminal 20 of the core unit 31 is given by the above equation 5,
  • V 01 -(1 + Cs Cf) ⁇ (R2 R 1) ⁇ (Vin A) (Equation 6), and the voltage V 02 of the AC output terminal 22 of the core 31 is calculated by the above equation 1.
  • V 02 -(R 2 / R 1)-(V in / A) (Equation 7)
  • the inverting section 32 is an inverting amplifier circuit including a variable resistor (R4) 40, a resistor (R5) 41, a variable resistor (R6) 42, a capacitor 43, and an operational amplifier 44.
  • the variable resistor (R4) 4 is set so that the gain is 1 and the phase of the signal V03 at its output terminal 23 is the same as the signal V02 at the AC output terminal 22 of the core unit 31.
  • the resistance values of 0 and the variable resistor (R6) 42 are adjusted. Therefore, the following relationship holds true between the input voltage V 01 and the output voltage V 03 of the inverting section 32.
  • V 03 -V 01 (Equation 8)
  • the adder 33 is an adder in which three resistors (R7) 45, resistors (R8) 46, and resistors (R9) 47 having the same resistance value are connected to the operational amplifier 48. That is, the following relationship is established between the voltages V 02 and V 03 of the two input signals and the output voltage V 04.
  • V 04 -(V 02+ V 03) (Equation 9)
  • V 04 V 01- V 02
  • the capacitance is obtained by the capacitance detection circuit 30 in the second embodiment.
  • the detection signal includes only a component proportional to the capacitance of the capacitor 17 to be detected, and includes an unnecessary offset (a voltage independent of the capacitor 17 to be detected). Not in. Therefore, the signal processing for specifying the capacitance of the capacitor 17 to be detected from the detection signal in the second embodiment is simple.
  • V03 —V01
  • V03 k ⁇ V01 (k is the gain of the inverting amplifier)
  • V 04 ⁇ k-(C s / C f) + (k + 1) ⁇ ⁇ (R 2 / R 1) ⁇ V in
  • FIG. 5 is a diagram showing an application example of the capacitance detection circuit in the first and second embodiments to an electronic device.
  • a cross-sectional view of a microphone 50 used for a mobile phone or the like in which a capacitor microphone and a capacitance detection circuit are integrated is shown.
  • the microphone 50 includes a lid 51 having a sound hole 52, a vibrating membrane 53 vibrating by sound, a ring 54 fixing the vibrating membrane 53, and a speaker 55.
  • a a fixed electrode 56 provided opposite the vibrating membrane 53 via the spacer 55a, an insulating plate 55b supporting the fixed electrode 56, and an insulating plate 55b.
  • the IC chip 58 fixed to the back surface and having the capacitance detection circuit of the above embodiment formed thereon, the IC package 59 molding the IC chip 58, the IC chip 58, and the like. It is composed of external electrodes 61a, 61b, etc. connected by bonding or the like.
  • the vibrating membrane 53 which is one of the electrodes forming the capacitor, is connected to a predetermined potential (ground in this example), and the fixed electrode 56, which is the other electrode, is made of an aluminum plate or wire bonding. It is connected to the circuit of the IC chip 58 through a conductor such as a contact hole.
  • the capacitance of the capacitor composed of the vibrating membrane 53 and the fixed electrode 56 or its change is detected by the capacitance detection circuit in the adjacent IC chip 58 via the insulating plate 55b, and is detected by the electric signal. It is converted and output from the external electrodes 6 1a.
  • the lid 51 is made of a metal such as aluminum, and has a conductive film (not shown) formed on the upper surface of the insulating substrate 60 as well as the internal capacitors 53, 56 and the IC chip 58. It plays a role as a shield box that blocks intrusion of disturbance noise.
  • the fixed electrode 56 and the circuit are connected to each other, and the vibrating membrane 53 is connected to a predetermined potential.
  • the vibrating membrane 53 and the circuit are connected to each other, and the fixed electrode 56 is connected to the predetermined potential. May be connected.
  • the former is preferred.
  • FIG. 6 is a schematic external view of the microphone 50 shown in FIG. Fig. 6 (a) is a plan view, Fig. 6 (b) is a front view, and Fig. 6 (c) is a bottom view.
  • the size of the lid 51 shown in FIGS. 6 (a) and 6 (b) is, for example, approximately 5 mm long and 2 mm high.
  • the four external electrodes 61 a to 61 d shown in FIG. 6C are, for example, two terminals for the power supply of the capacitance detection circuit and two terminals for the output signal.
  • the capacitor to be detected (here, a capacitor microphone) and the capacitance detection circuit (here, an IC chip) are provided adjacent to each other, and the signal line is extremely short.
  • Capacitor microphone Capacitor microphone or first impedance element in circuit, whichever is greater It is connected by a conductor whose length does not exceed 10 times the quantity value.
  • a shield member such as a metal lid. Therefore, in such an application example, it is considered that adverse effects such as disturbance noise mixed in the signal line (conductor) connecting the capacitor to be detected and the capacitance detection circuit can be ignored.
  • the capacitor to be detected and the capacitance detection circuit are connected by an extremely short conductor.
  • Providing a special circuit for applying a guard voltage to the gate rather increases the circuit scale and prevents the circuit from being compact. Therefore, the shortest path between the capacitor to be detected and the capacitance detection circuit should be connected by a non-shielded (unshielded) conductive plate, wiring pattern, wire bonding, lead wire, etc.
  • Figs. 7 and 8 show the circuit mounted on a board. This is basically the same as the above embodiment except that the capacitance detection circuit is mounted on the substrate 62.
  • the capacitance detection circuit according to the present invention has been described based on the two embodiments and the application to the product. However, the present invention is limited to these embodiments and the application. is not.
  • a capacitor 15 is connected between the operational amplifier 14 and the impedance converter 16 to detect the current flowing through the capacitor 17 to be detected.
  • an impedance element such as a resistor or an inductance.
  • a resistor 18 may be added in parallel with the capacitor 15 in the capacitance detection circuits 10 and 30 in the above embodiment and connected. As a result, the connection point between the capacitor 15 and the capacitor 17 to be detected is connected to the output terminal of the first operational amplifier 14 via the resistor 18. As a result, the DC floating state is eliminated, and the potential is fixed.
  • the capacitive sensors connected as the detected capacitors 17 are not limited to capacitor microphones, but also include acceleration sensors, seismometers, pressure sensors, displacement sensors, displacement meters, proximity sensors, touch sensors, and ion sensors. Sensor, humidity sensor, raindrop sensor, snow sensor, lightning sensor, alignment sensor, poor contact sensor, shape sensor, end point detection sensor, vibration sensor, ultrasonic sensor, angular velocity sensor, liquid level sensor, gas sensor, infrared sensor, Radiation sensors, water level gauges, freeze sensors, moisture meters, vibrometers, charge sensors, well-known capacitive sensors such as printed circuit board inspection machines, etc., all of which detect various physical quantities using changes in capacitance Of transducers (devices).
  • the capacitance detection circuit, the capacitance detection device, and the microphone device apply the AC voltage to the operational amplifier via the resistor, and apply the detected voltage to the signal line.
  • the capacitance of the capacitor to be detected is detected by connecting a capacitor. That is, a capacitor is connected between the output terminal of the operational amplifier whose non-inverting input terminal is connected to the predetermined potential and the input terminal of the impedance converter, and the input terminal of the impedance converter is connected to the predetermined potential.
  • the detected capacitor is connected between them.
  • the non-inverting input terminal of the operational amplifier is connected to a predetermined potential, and one potential of the input terminal is fixed, so that the operational amplifier operates stably, the operational error is reduced, and the detection signal is reduced. Included noise is suppressed.
  • a capacitor is connected between the operational amplifier and the impedance converter.
  • the capacitance detection circuit and the capacitor to be detected may be provided adjacent to each other, or a circuit element connected to the signal line may be provided close to the capacitance detection circuit, and a shielded cable may be connected between them. Also, there is no need for a special circuit to cancel the stray capacitance generated in the cable.
  • an inverting amplifier circuit for inverting the signal at the signal output terminal and an adding circuit for adding the output signal of the impedance converter and the output signal of the inverting amplifier circuit are added to the capacitance detecting circuit. You may. As a result, unnecessary offset components included in the output signal of the capacitance detection circuit are removed, and a net signal corresponding to the capacitance of the detected capacitor can be greatly amplified.
  • the capacitor to be detected is a condenser microphone, and the capacitance detection circuit is realized by an IC.
  • the condenser microphone and the IC are integrated into one microphone as a microphone used in mobile phones and the like. Since the capacitor microphone and the capacitance detection circuit are placed very close to each other by being housed in a housing (shield box), the capacitor to be detected and the capacitance detection circuit are connected to each other. A special circuit, etc. for applying a large-diameter shield cap lug guard voltage is not required.
  • the capacitance detection circuit detects the capacitance by applying a current to the capacitor to be detected
  • the capacitance of the capacitor to be detected is, for example, an electret capacitor microphone. There is no need to attach a polymer film or the like to the Can be applied to sensors.
  • the capacitance detection circuit according to the present invention can be used as a detection circuit of a capacitive sensor, particularly as a microphone device provided in a small and lightweight device such as a mobile phone.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Measurement Of Resistance Or Impedance (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)

Abstract

A capacitance measuring circuit (10) comprising an AC voltage generator (11), an operational amplifier (14) having a noninverted input terminal connected to a predetermined potential (in this example, to the ground), an impedance converter (16), a resistor (R1) (12) connected between the AC voltage generator (11) and the inverted input terminal of the operational amplifier (14), a resistor (R2) (13) connected between the inverted output terminal of the operational amplifier (14) and the output terminal of the impedance converter (16), and an impedance element (capacitor) (15) connected between the output terminal of the operational amplifier (14) and the input terminal of the impedance converter (16), wherein a capacitor (17) to be measured is connected between the input terminal of the impedance converter (16) and a predetermined potential, and the capacitor measuring circuit (10) is provided in a position adjacent to the capacitor (17) to be measured.

Description

明 細 書 静電容量検出回路、 静電容量検出装置及びマイク ロホン装置 技術分野  Description Capacitance detection circuit, capacitance detection device, and microphone device
本発明は、 静電容量を検出する回路及び装置等に関し、 特に、 微小な 容量を高い精度で検出する回路、 装置及びマイク ロホン装置に関する。 背景技術  The present invention relates to a circuit and a device for detecting a capacitance, and more particularly to a circuit, a device and a microphone device for detecting a minute capacitance with high accuracy. Background art
静電容量検出回路の従来例と して、 特開平 9一 2 8 0 8 0 6号公報記 載のものを挙げることができる。 図 1 は、 この静電容量検出回路を示す 回路図である。 この検出回路では、 電極 9 0、 9 1 で形成される容量セ ンサ 9 2が、 信号線 9 3 を介して演算増幅器 9 5の反転入力端子に接続 されている。 そ してこの演算増幅器 9 5の出力端子と前記反転入力端子 との間にコ ンデンサ 9 6が接続されると ともに、 非反転入力端子に交流 電圧 V acが印加されている。 また信号線 9 3はシール ド線 9 4によって 被覆され、 外乱ノ イズに対して電気的に遮蔽されている。 そしてこのシ 一ル ド線 9 4は、 演算増幅器 9 5の非反転入力端子に接続されている。 出力電圧 V dは、 演算増幅器 9 5の出力端子から 卜ランス 9 7 を介して 取り出される。  As a conventional example of the capacitance detection circuit, there is a circuit described in Japanese Patent Application Laid-Open No. Hei 9-1280806. FIG. 1 is a circuit diagram showing this capacitance detection circuit. In this detection circuit, a capacitance sensor 92 formed by the electrodes 90 and 91 is connected to an inverting input terminal of an operational amplifier 95 via a signal line 93. The capacitor 96 is connected between the output terminal of the operational amplifier 95 and the inverting input terminal, and the AC voltage Vac is applied to the non-inverting input terminal. The signal line 93 is covered with a shield line 94 and is electrically shielded from disturbance noise. The shield wire 94 is connected to the non-inverting input terminal of the operational amplifier 95. The output voltage Vd is taken out from the output terminal of the operational amplifier 95 via the transformer 97.
この検出回路では、 演算増幅器 9 5の反転入力端子と非反転入力端子 とがィマージナリ ショー トの状態となり、 反転入力端子に接続された信 号線 9 3 と非反転入力端子に接続されたシール ド線 9 4 とは、 互いにほ ぼ同電位となる。 これによつて、 信号線 9 3はシール ド線 9 4によって ガーデイ ングされ、 つまり、 両者 9 3 、 9 4間の浮遊容量はキャンセル され、 浮遊容量に影響されにく い出力電圧 V d が得られるというもので ある。 In this detection circuit, the inverting input terminal and the non-inverting input terminal of the operational amplifier 95 are in the state of image short, and the signal line 93 connected to the inverting input terminal and the shield line connected to the non-inverting input terminal 9 4 have almost the same potential as each other. As a result, the signal line 93 is guarded by the shield line 94, that is, the stray capacitance between the two is canceled, and an output voltage Vd which is hardly influenced by the stray capacitance is obtained. That can be is there.
しかしながら、 このよ うな従来技術によれば、 確かに容量センサ 9 2 の容量がある程度に大きいときは信号線 9 3 とシール ド線 9 4 との間の 浮遊容量に影響されない正確な出力電圧 V d を得ることができるものの 数 p Fあるいは f F (フヱム トファラッ ド) オーダー以下の微小な容量 の検出においては、 誤差が大きく なつてしまう という問題がある。  However, according to such a conventional technique, when the capacitance of the capacitance sensor 92 is large to some extent, an accurate output voltage V d which is not affected by the stray capacitance between the signal line 93 and the shield line 94 is certainly obtained. However, there is a problem that the error increases when detecting a very small capacitance of the order of several pF or fF (femto-Farad).
また、 印加する交流電圧 V acの周波数によっては、 演算増幅器 9 5の 内部の トラッキングエラ一等によ り、 ィマージナリ ショー トの状態にあ る反転入力端子と非反転入力端子の電圧間にも結果的に微妙な位相 · 振 幅のズレが発生し、 検出誤差が大き く なつて しまう という問題もある。 一方、 携帯電話機等に代表される軽量 · 小型の音声通信機器において は、 コ ンデンサマイク ロホン等の容量センサで検出した音声を、 高感度 かつ忠実に電気信号に変換するコ ンパク トな増幅回路が求められている, 数 p Fあるいは f Fオーダ一以下の微小な容量又はその変化を正確に検 出することができるならば、 極めて高い感度で、 かつ、 忠実に音声を検 出することが可能な高性能なマイク ロホンが実現され、 携帯電話機等の 音声通信機器での音声のピックアップにおける性能が飛躍的に向上され る。  Also, depending on the frequency of the applied AC voltage V ac, the tracking error in the operational amplifier 95 may cause a difference between the voltage at the inverting input terminal and the voltage at the non-inverting input terminal in the marginal short state. There is also a problem that the phase and amplitude shifts are delicate in nature, and the detection error increases. On the other hand, in light and small voice communication devices such as mobile phones, a compact amplifier circuit that converts voice detected by a capacitive sensor such as a capacitor microphone into an electrical signal with high sensitivity and high fidelity is required. If it is possible to accurately detect the required small capacitance of the order of several pF or fF or less or its change, it will be possible to detect sound with extremely high sensitivity and faithfulness A high-performance microphone is realized, and the performance of voice pickup in voice communication devices such as mobile phones is dramatically improved.
そこで、 この発明は、 このような状況に鑑みてなされたものであり、 微小な容量を正確に検出することができ、 かつ、 軽量 ■ 小型の音声通信 機器に使用されるコンデンサマイク ロホン等の容量センサの容量検出に 適した静電容量検出回路等を提供することを目的とする。 発明の開示  Accordingly, the present invention has been made in view of such a situation, and is capable of accurately detecting a minute capacitance, and is lightweight. ■ The capacitance of a condenser microphone or the like used in a small-sized voice communication device. It is an object of the present invention to provide a capacitance detection circuit or the like suitable for detecting the capacitance of a sensor. Disclosure of the invention
上記目的を達成するために、 本発明に係る静電容量検出回路は、 被検 出コ ンデンサの静電容量に対応する検出信号を出力する静電容量検出回 路であって、 入力イ ンピ一ダンスが高く 出力イ ンピーダンスが低いイン ピ一ダンス変換器と、 容量性の第 1 イ ンピ一ダンス素子と、 演算増幅器 と、 前記演算増幅器に交流電圧を印加する交流電圧発生器と、 前記演算 増幅器の出力に接続される信号出力端子とを備え、 前記イ ンピーダンス 変換器の入力端子には前記被検出コ ンデンサの一端と前記第 1 イ ンピ一 ダンス素子の一端とが接続され、 前記演算増幅器の負帰還路に前記第 1 イ ンピーダンス素子及び前記イ ンピーダンス変換器が含まれ、 前記被検 出コ ンデンサと前記静電容量検出回路とは隣接して設けられていること を特徴とする。 In order to achieve the above object, a capacitance detection circuit according to the present invention includes a capacitance detection circuit that outputs a detection signal corresponding to the capacitance of a capacitor to be detected. An impedance converter having a high input impedance and a low output impedance, a capacitive first impedance element, an operational amplifier, and applying an AC voltage to the operational amplifier. An AC voltage generator; and a signal output terminal connected to an output of the operational amplifier. An input terminal of the impedance converter has one end of the capacitor to be detected and one end of the first impedance element. The first impedance element and the impedance converter are included in a negative feedback path of the operational amplifier, and the detection capacitor and the capacitance detection circuit are provided adjacent to each other. It is characterized by having.
また、 本発明に係る静電容量検出回路は、 被検出コ ンデンサの静電容 量に対応する検出信号を出力する静電容量検出回路であって、 入力イン ピーダンスが高く 出力イ ンピーダンスが低いイ ンピーダンス変換器と、 容量性の第 1 インピーダンス素子と、 演算増幅器と、 前記演算増幅器に 交流電圧を印加する交流電圧発生器と、 前記演算増幅器の出力に接続さ れる信号出力端子とを備え、 前記イ ンピ一ダンス変換器の入力端子には 前記被検出コンデンサの一端と前記第 1 インピーダンス素子の一端とが 接続され、 前記演算増幅器の負帰還路に前記第 1 イ ンピーダンス素子及 び前記イ ンピーダンス変換器が含まれ、 前記被検出コ ンデンサと前記第 1 イ ンピーダンス素子と前記イ ンピーダンス変換器とが近接して設けら れていることを特徴とする。  Further, the capacitance detection circuit according to the present invention is a capacitance detection circuit that outputs a detection signal corresponding to the capacitance of a capacitor to be detected, wherein the input impedance is high and the output impedance is low. A converter, a capacitive first impedance element, an operational amplifier, an AC voltage generator for applying an AC voltage to the operational amplifier, and a signal output terminal connected to an output of the operational amplifier. One end of the capacitor to be detected and one end of the first impedance element are connected to an input terminal of the impedance converter, and the first impedance element and the impedance converter are connected to a negative feedback path of the operational amplifier. Wherein the detected capacitor, the first impedance element, and the impedance converter are provided close to each other. And features.
具体例と しては、 交流電圧発生器と、 非反転入力端子が所定の電位に 接続された演算増幅器と、 イ ンピーダンス変換器と、 演算増幅器の反転 入力端子とインピーダンス変換器の出力端子間に接続される抵抗と、 演 算増幅器の出力端子とイ ンピーダンス変換器の入力端子間に接続される コンデンサ (第 1 イ ンピーダンス素子) とを備える静電容量検出回路を 構成し、 被検出コ ンデンサはイ ンピーダンス変換器の入力端子と所定の 電位間に接続し、静電容量検出回路と被検出コンデンサとは隣接、又は、 信号線の浮遊容量が接続される素子の容量の最大の値の 1 0倍を超えな いよ うに短く 近接した位置に設けておく 。 ここで、 所定の電位とは、 あ る基準電位、 所定の直流電位、 接地電位またはフローティ ング状態のい ずれかを指すものであり、 実施の態様にあわせて最適なものが選択され る。 なお、 さ らに交流電圧発生器と演算増幅器の反転入力端子間に接続 される第 2イ ンピーダンスと しての抵抗を設けても良い。 Specific examples include an AC voltage generator, an operational amplifier whose non-inverting input terminal is connected to a predetermined potential, an impedance converter, and a circuit between the inverting input terminal of the operational amplifier and the output terminal of the impedance converter. The capacitance detection circuit comprises a connected resistor and a capacitor (first impedance element) connected between the output terminal of the operational amplifier and the input terminal of the impedance converter. The input terminal of the impedance converter Connected between potentials, the capacitance detection circuit and the capacitor to be detected are adjacent, or short and close so that the stray capacitance of the signal line does not exceed 10 times the maximum value of the capacitance of the connected element To be provided. Here, the predetermined potential refers to any one of a certain reference potential, a predetermined DC potential, a ground potential, and a floating state, and an optimum one is selected according to the embodiment. In addition, a resistor as a second impedance connected between the AC voltage generator and the inverting input terminal of the operational amplifier may be provided.
このよ うな構成によって、 被検出コ ンデンサに一定の電圧が印加され ると ともに、 その被検出コンデンサに流れる電流のほとんど全てがコ ン デンサ (第 1 イ ンピ一ダンス素子) に流れ、 信号出力端子からは、 被検 出コ ンデンサの静電容量に対応した信号が出力される。  With this configuration, a constant voltage is applied to the capacitor to be detected, and almost all the current flowing through the capacitor to be detected flows to the capacitor (first impedance element), and the signal output terminal Outputs a signal corresponding to the capacitance of the detected capacitor.
なお、 静電容量検出回路と被検出コンデンサとを接続する信号線への ノ イズの混入や、 その信号線の浮遊容量の発生を低減させるために、 被 検出コ ンデンサと静電容量検出回路とは可能な限り隣接した位置に設け ておく 。 または、 被検出コンデンサと第 1 イ ンピーダンス素子とイ ンピ In order to reduce noise in the signal line connecting the capacitance detection circuit and the capacitor to be detected, and to reduce the occurrence of stray capacitance in the signal line, the capacitor to be detected and the capacitance detection circuit must be connected to each other. Should be provided as close as possible to each other. Or, the capacitor to be detected, the first impedance element, and the impedance
—ダンス変換器とが可能な限り近接した位置に設けておく 。 — Install it as close to the dance converter as possible.
ここで、本願明細書において、「近接する jとは、信号線の浮遊容量が、 被検出コ ンデンサの容量値又は容量性の第 1 イ ンピーダンス素子の容量 値の大きい方の容量値に対して 1 0倍を超えない状態にあることをいう これは、 信号線の浮遊容量が、 接続されている素子の容量値の一桁上の 数値を超えない容量値と したときに、 本発明の静電容量検出回路は、 検 出感度の大幅な悪化を防ぐことができるという ことが分かったものであ リ、 これは経験的に得られたものである。 この信号線の浮遊容量は、 被 検出コンデンサと、 第 1 イ ンピーダンス素子と、 イ ンピーダンス変換器 とを信号線に接続しない状態で、容量測定を行えば測定できる。そして、 本願明細書では、上記の近接した条件で隣り合って接している状態を「隣 接」 という。 Here, in the specification of the present application, “nearly j” means that the stray capacitance of the signal line is larger than the capacitance value of the capacitance of the capacitor to be detected or the capacitance value of the capacitive first impedance element. This means that the stray capacitance of the signal line does not exceed the one-digit value of the capacitance value of the connected element. It has been found that the capacitance detection circuit can prevent the detection sensitivity from significantly deteriorating, and this has been obtained empirically. The capacitance can be measured by measuring the capacitance without connecting the capacitor, the first impedance element, and the impedance converter to the signal line. The state Contact.
ここで、 前記静電容量検出回路に加えて、 信号出力端子での信号を反 転する反転増幅回路と、 イ ンピーダンス変換器の出力信号と反転増幅回 路の出力信号とを加算する加算回路と を付加してもよい。 また、 コンデ ンサ(第 1 イ ンピ一ダンス素子)と並列に抵抗を接続しておいてもよい。 また、 本発明の応用と して、 被検出コ ンデンサは、 容量の変化に応じ て物理量を検出する容量型センサと し、 静電容量検出回路は、 プリ ン ト 基板又はシリ コン基板上に形成し、 それら容量型センサと基板とを固定 する、 も しく は、 一体成形しているものが好ましい。 さ らに具体例と し て、 よ り好ましく は、 被検出コンデンサと して、 コ ンデンサマイク ロホ ンを採用し、 静電容量検出回路については I Cで実現し、 それらコ ンデ ンサマイク と I Cとを一体化し、 携帯電話機等に使用されるマイク ロホ ンと して 1 つの筐体 (シール ドボックス) に収めてもよい。 このとき、 コ ンデンサマイク ロホンと I Cとは隣接した位置に固定し、導電性の板、 配線パターン、 ワイヤボンディ ング等で接続しておく 。 図面の簡単な説明  Here, in addition to the capacitance detecting circuit, an inverting amplifier circuit for inverting a signal at a signal output terminal, an adding circuit for adding an output signal of the impedance converter and an output signal of the inverting amplifier circuit, May be added. Further, a resistor may be connected in parallel with the capacitor (first impedance element). Further, as an application of the present invention, the detected capacitor is a capacitive sensor that detects a physical quantity according to a change in capacitance, and the capacitance detecting circuit is formed on a printed circuit board or a silicon substrate. However, it is preferable that the capacitive sensor and the substrate are fixed, or that they are integrally formed. As a more specific example, more preferably, a capacitor microphone is used as the capacitor to be detected, and the capacitance detection circuit is realized by an IC, and the capacitor microphone and the IC are used. May be integrated and housed in a single case (shielded box) as a microphone used for mobile phones and the like. At this time, the capacitor microphone and the IC are fixed at adjacent positions, and are connected by a conductive plate, a wiring pattern, a wire bonding, or the like. BRIEF DESCRIPTION OF THE FIGURES
図 1 は、 従来の静電容量検出回路の回路図である。  FIG. 1 is a circuit diagram of a conventional capacitance detection circuit.
図 2は、 本発明の第 1 の実施の形態における静電容量検出回路の回路 図である。  FIG. 2 is a circuit diagram of the capacitance detection circuit according to the first embodiment of the present invention.
図 3は、 ( a ) 〜 ( e ) は、 本発明で使用可能なイ ンピーダンス変換器 の例を示す図である。  FIGS. 3A to 3E show examples of impedance converters usable in the present invention.
図 4は、 本発明の第 2の実施の形態における静電容量検出回路の回路 図である。  FIG. 4 is a circuit diagram of a capacitance detection circuit according to the second embodiment of the present invention.
図 5は、本発明の静電容量検出回路の電子機器への応用例を示す図(マ イク 口ホンの断面図) である。 図 6は、 図 4に示されたマイク ロホンの概略的な外観図であり、 ( a ) は平面図、 ( b ) は正面図、 ( c ) は底面図である。 FIG. 5 is a diagram (a cross-sectional view of a microphone) showing an application example of the capacitance detection circuit of the present invention to an electronic device. FIG. 6 is a schematic external view of the microphone shown in FIG. 4, in which (a) is a plan view, (b) is a front view, and (c) is a bottom view.
図 7 は、 マイク ロホンの他の一例の断面図である。  FIG. 7 is a cross-sectional view of another example of the microphone.
図 8は、 図 6に示されたマイク ロホンの概略的な外観図であり、 ( a ) は平面図、 ( b ) は正面図である。  FIG. 8 is a schematic external view of the microphone shown in FIG. 6, in which (a) is a plan view and (b) is a front view.
図 9は、 本発明の他の実施の形態における静電容量検出回路の回路図 である。 発明を実施するための最良の形態  FIG. 9 is a circuit diagram of a capacitance detection circuit according to another embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION
以下、 本発明の実施の形態について、 図面を用いて詳細に説明する。 (第 1 の実施の形態)  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. (First Embodiment)
図 2は、 本発明の第 1 の実施の形態例における静電容量検出回路 1 0 の回路図である。 なお、 本図では、 この静電容量検出回路 1 0に、 検出 対象である被検出コンデンサ 1 7 (ここでは、 コ ンデンサマイク ロホン 等、 静電容量 Csの変化を利用して各種物理量を検出する容量型センサ) が接続されている。  FIG. 2 is a circuit diagram of the capacitance detection circuit 10 according to the first embodiment of the present invention. In this figure, the capacitance detection circuit 10 has a capacitor 17 to be detected (here, a capacitor microphone, etc., which detects various physical quantities by using a change in the capacitance Cs). (Capacitive sensor) is connected.
この静電容量検出回路 1 0は、 交流電圧を発生する交流電圧発生器 1 1 、 抵抗 ( R 1) 1 2、 抵抗 ( R2) 1 3、 演算増幅器 1 4、 イ ンピーダ ンス素子 (ここでは、 容量 Cf のコ ンデンサ) 1 5及びイ ンピーダンス 変換器 1 6から構成され、 被検出コ ンデンサ 1 7の静電容量に対応する 検出信号 (電圧 V out) を信号出力端子 2 0から出力する。  The capacitance detection circuit 10 includes an AC voltage generator 11 for generating an AC voltage, a resistor (R1) 12, a resistor (R2) 13, a operational amplifier 14, and an impedance element (here, It consists of a capacitor (capacitor Cf) 15 and an impedance converter 16, and outputs a detection signal (voltage V out) corresponding to the capacitance of the capacitor 17 to be detected from the signal output terminal 20.
交流電圧発生器 1 1 は、 一端が所定の電位 (本例では、 接地) に接続 され、 他端 (出力端子) から一定の交流電圧 (電圧 Vin、 角周波数 ω) を発生している。 交流電圧発生器 1 1 の出力端子と演算増幅器 1 4の反 転入力端子との間には抵抗 ( R 1) 1 2が接続されている。  One end of the AC voltage generator 11 is connected to a predetermined potential (ground in this example), and a constant AC voltage (voltage Vin, angular frequency ω) is generated from the other end (output terminal). A resistor (R 1) 12 is connected between the output terminal of the AC voltage generator 11 and the inverted input terminal of the operational amplifier 14.
演算増幅器 1 4は、 入力インピーダンス及び開ループゲインが極めて 高い電圧増幅器であり、 ここでは、 非反転入力端子が所定の電位 (本例 では、 接地) に接続され、 非反転入力端子及び反転入力端子がィマージ ナリ ショー 卜の状態となつている。 この演算増幅器 1 4の負帰還路、 つ ま り、 演算増幅器 1 4の出力端子から反転入力端子までの間に、 コンデ ンサ 1 5 、 イ ンピーダンス変換器 1 6及び抵抗 ( R 2 ) 1 3がこの順で 直列に接続されている。 Operational amplifier 14 has extremely high input impedance and open loop gain. This is a high voltage amplifier, in which the non-inverting input terminal is connected to a predetermined potential (ground in this example), and the non-inverting input terminal and the inverting input terminal are in the state of imagery short. The capacitor 15, the impedance converter 16, and the resistor (R 2) 13 are connected between the negative feedback path of the operational amplifier 14, that is, between the output terminal and the inverting input terminal of the operational amplifier 14. They are connected in series in this order.
イ ンピーダンス変換器 1 6は、 入力イ ンピーダンスが極めて高く 、 出 力イ ンピーダンスが極めて低く 、電圧ゲインが A倍の電圧増幅器である。 このィンピ一ダンス変換器 1 6の入力端子 2 1 には、 信号線又はプリ ン ト基板上の配線パターン等の導電体を介して、 被検出コ ンデンサ 1 7の —端が接続され、一方、 被検出コ ンデンサ 1 7の他端は、 所定の電位 (本 例では、 接地) に接続されている。 演算増幅器 1 4の出力端子には、 こ の静電容量検出回路 1 0の出力信号、 つまり、 被検出コ ンデンサ 1 7の 容量に対応した検出信号を出力するための信号出力端子 2 0が接続され ている。 なお、 本願では、 A倍等に示される変数 Aはいずれも零 ( 0 ) 以外の実数を表す。  The impedance converter 16 is a voltage amplifier whose input impedance is extremely high, whose output impedance is extremely low, and whose voltage gain is A times. The input terminal 21 of the impedance converter 16 is connected to the negative terminal of the detected capacitor 17 via a conductor such as a signal line or a wiring pattern on a printed circuit board. The other end of the capacitor 17 to be detected is connected to a predetermined potential (ground in this example). The output terminal of the operational amplifier 14 is connected to the output signal of the capacitance detection circuit 10, that is, the signal output terminal 20 for outputting the detection signal corresponding to the capacitance of the capacitor 17 to be detected. It has been. In the present application, each of the variables A indicated by A times or the like represents a real number other than zero (0).
なお、 被検出コ ンデンサ 1 7 と静電容量検出回路 1 0 との接続につい て、 不要な浮遊容量が検出誤差と して加算されたり、 外乱ノイズが混入 したりすることを避けるために、 可能な限り短い導電体 (ケーブル、 銅 箔の配線パターン、 接続端子など) で接続するのが好ま しい。 さ らに、 可能ならば、 外乱ノ イズに対する遮蔽を強化するために、 被検出コ ンデ ンサ 1 7及び静電容量検出回路 1 0全体を接地されたシール ド部材で覆 つたり、 シール ドボックス内に収納するのが好ま しい。  Note that the connection between the capacitor 17 to be detected and the capacitance detection circuit 10 is possible in order to prevent unnecessary stray capacitance from being added as a detection error or from being mixed with disturbance noise. It is preferable to connect with the shortest conductor (cable, copper foil wiring pattern, connection terminal, etc.). In addition, if possible, cover the detected capacitor 17 and the capacitance detecting circuit 10 entirely with a grounded shield member, or provide a shield to enhance the shielding against disturbance noise. It is preferable to store it in a box.
以上のように構成された静電容量検出回路 1 0の動作は以下の通りで ある。  The operation of the capacitance detection circuit 10 configured as described above is as follows.
抵抗 ( R 1 ) 1 2、 抵抗 ( R 2 ) 1 3及び演算増幅器 1 4等から構成さ れる反転増幅回路に着目すると、 演算増幅器 1 4の両入力端子がイマ一 ジナリ ショー トの状態となって同電位 (例えば、 0 V ) であり、 かつ、 その入力インピーダンスが極めて高く 、 電流が流れないことから、 抵抗 ( R 1) 1 2 を流れる電流は、 Vin/ R 1 となり、 その全てが抵抗 ( R 2) 1 3 を流れるので、 インピーダンス変換器 1 6の出力電圧を V2 とする と、 It consists of resistance (R 1) 12, resistance (R 2) 13 and operational amplifier 14 Focusing on the inverting amplifier circuit, both input terminals of the operational amplifier 14 are in an imaginary short state and are at the same potential (for example, 0 V), and their input impedance is extremely high. Therefore, the current flowing through the resistor (R 1) 1 2 is Vin / R 1, and all of the current flows through the resistor (R 2) 13.Therefore, if the output voltage of the impedance converter 16 is V2,
V inZ R l= - V2/ R2  V inZ R l =-V2 / R2
が成リ立つ。 これを整理することによ り、 インピ一ダンス変換器 1 6 の出力電圧 V 2は、  Is established. By rearranging this, the output voltage V 2 of the impedance converter 16 becomes
V 2= - ( R 2/ R 1) - V in (式 1 )  V 2 =-(R 2 / R 1)-V in (Equation 1)
となる。 また、 イ ンピーダンス変換器 1 6の電圧ゲイ ンは Aであるの で、 入力電圧 (入力端子 2 1 の電圧) V I と出力電圧 (出力端子 2 2で の電圧) V2 との関係よ り、 その入力電圧 V I は、  Becomes In addition, since the voltage gain of the impedance converter 16 is A, the relationship between the input voltage (the voltage at the input terminal 21) VI and the output voltage (the voltage at the output terminal 22) V2 indicates that The input voltage VI is
V 1= ( 1 / A ) ■ V 2 (式 2 )  V 1 = (1 / A) ■ V 2 (Equation 2)
が成り立つ。 また、 コ ンデンサ 1 5を被検出コ ンデンサ 1 7に向かつ て流れる電流を i とすると、 インピーダンス変換器 1 6の入力イ ンピー ダンスが極めて高いことから、 その電流 i の全てが被検出コンデンサ 1 7に流れるので、 電流 i は、 j ω C s · V I となり、 信号出力端子 2 0 から出力される検出信号の電圧 V outは、  Holds. Further, if the current flowing through the capacitor 15 toward the capacitor 17 to be detected is i, the input impedance of the impedance converter 16 is extremely high. 7, the current i becomes jωCs · VI, and the voltage Vout of the detection signal output from the signal output terminal 20 is
V out= i ■ ( 1 / j ω C f ) + V 1  V out = i ■ (1 / j ω C f) + V 1
= ( 1 + Cs/ Cf) ■ V 1 (式 3 )  = (1 + Cs / Cf) ■ V 1 (Equation 3)
となる。  Becomes
上記式 1 と式 2 とから、 V2 を消去すると、  From the above equations 1 and 2, when V2 is eliminated,
V 1= - ( R2 R 1) ■ ( Vin/ A ) (式 4 )  V 1 =-(R2 R 1) ■ (Vin / A) (Equation 4)
が得られ、 この V 1 を上記式 3に代入すると、  Is obtained. By substituting this V 1 into Equation 3 above,
V out= - ( 1 + C s/ C f) - ( R 2/ R 1) - ( V in/ A ) (式 5 ) が得られる。 V out =-(1 + C s / C f)-(R 2 / R 1)-(V in / A) (Equation 5) Is obtained.
この式 5から分かるように、 静電容量検出回路 1 0の信号出力端子 2 0から出力される検出信号の電圧 V out は、 被検出コ ンデンサ 1 7の容 量 C sに依存した値となる。 従って、 この電圧 V outに対して種々の信号 処理を施すことによって、 容量 C s を特定することができる。 また、 こ の式 5には角周波数 ωが含まれていないことから分かるように、 この検 出信号の電圧 V out は、 交流電圧発生器 1 1 からの交流信号 V inの周波 数及び被検出コ ンデンザの周波数の変化に依存しない。 これによつて、 被検出コ ンデンサ 1 7 に印加される交流電圧の周波数に依存することな く 、 被検出コ ンデンサ 1 7の容量を検出することができる (回路での周 波数依存特性を有しない)静電容量検出回路が実現される。したがって、 コンデンサマイク ロホン等、 容量値がある周波数 (音声帯域) で変化す るような被検出コンデンサ 1 7 に対して、 検出された信号を周波数補正 することなく 、 その電圧値から直接、 容量値を特定することが可能とな る。  As can be seen from Equation 5, the voltage Vout of the detection signal output from the signal output terminal 20 of the capacitance detection circuit 10 depends on the capacitance Cs of the capacitor 17 to be detected. . Therefore, by performing various signal processing on the voltage Vout, the capacitance Cs can be specified. Further, as can be seen from the fact that this equation 5 does not include the angular frequency ω, the voltage V out of the detection signal is equal to the frequency of the AC signal Vin from the AC voltage generator 11 and the frequency of the detected signal. It does not depend on changes in the capacitor frequency. As a result, the capacitance of the capacitor 17 to be detected can be detected without depending on the frequency of the AC voltage applied to the capacitor 17 to be detected. No) A capacitance detection circuit is realized. Therefore, for a capacitor 17 such as a condenser microphone whose capacitance value changes at a certain frequency (voice band), the capacitance value can be calculated directly from its voltage value without frequency correction of the detected signal. Can be specified.
また、 本実施の形態例の静電容量検出回路 1 0では、 コ ンデンサ 1 5 及び被検出コ ンデンサ 1 7 に電流を供給している演算増幅器 1 4は、 そ の非反転入力端子が所定の電位に接続され、 固定化されている。 したが つて、 図 1 に示される従来の回路における演算増幅器 9 5 と異なり、 演 算増幅器 1 4は、 入力される交流信号の周波数等に依存することなく 、 ノ イズの少ない安定した電流をコンデンサ 1 5及び被検出コ ンデンサ 1 7に供給するので、 被検出コンデンサ 1 7の微小な容量の検出が可能と なる。  Also, in the capacitance detection circuit 10 of the present embodiment, the operational amplifier 14 that supplies current to the capacitor 15 and the capacitor 17 to be detected has a non-inverting input terminal having a predetermined value. Connected to the potential and fixed. Therefore, unlike the operational amplifier 95 in the conventional circuit shown in FIG. 1, the operational amplifier 14 supplies a stable current with little noise without depending on the frequency of the input AC signal. Since the voltage is supplied to the capacitor 15 and the capacitor 17 to be detected, the minute capacitance of the capacitor 17 to be detected can be detected.
なお、 本発明に関する実験によれば、 図 2の静電容量検出回路におい て、 例えば、 C s (被検出コンデンサ : 本実施の形態ではマイク ロホン) の元々の静電容量が 2 0 p Fのときに、 信号線の浮遊容量が 2 0 0 p F を越すと、 かなり検出感度が悪化した。 また、 前記 C sについて、 いく つかの別の静電容量値で確認したと ころ、 同じ傾向の結果を得た。 According to the experiment on the present invention, in the capacitance detecting circuit of FIG. 2, for example, the original capacitance of C s (capacitor to be detected: microphone in this embodiment) is 20 pF. When the stray capacitance of the signal line is 200 pF Beyond, the detection sensitivity deteriorated considerably. Further, when the above Cs was confirmed at several different capacitance values, the same tendency was obtained.
また、 第 1 イ ンピーダンス素子である容量 C f と被検出コンデンサ C s とは、 この回路中ではともに信号線に接続された容量素子であり、 ど ちらの素子についてみても計算上は前記と同じ結果をもたらすものと考 えられる。  The capacitance C f and the detected capacitor C s, which are the first impedance element, are both capacitance elements connected to the signal line in this circuit, and the calculation is the same as above for both elements. It is likely to have consequences.
これらの実験結果及び経験から、 信号線の浮遊容量が、 当該 C s又は C f の容量値の一桁上の値を越えないように、 被検出コンデンサと第 1 インピーダンス素子とイ ンピーダンス変換器とを近接させると良好な検 出感度が得られることが分かった。  From these experimental results and experience, the detected capacitor, the first impedance element, and the impedance converter should be connected so that the stray capacitance of the signal line does not exceed the value of the capacitance of the relevant Cs or Cf by one order of magnitude. It was found that good detection sensitivity could be obtained when the distances were close to each other.
図 3は、 図 2に示された静電容量検出回路 1 0におけるインピ一ダン ス変換器 1 6の具体的な回路例を示す。 図 3 ( a ) は、 演算増幅器 1 0 0を用いたボルテージフォロワを示している。 演算増幅器 1 0 0の反転 入力端子と出力端子とが短絡されている。 この演算増幅器 1 0 0の非反 転入力端子をイ ンピーダンス変換器 1 6の入力と し、 演算増幅器 1 0 0 の出力端子をイ ンピーダンス変換器 1 6の出力とすることで、 入力イン ピーダンスが極めて高く 、 電圧ゲイ ン Aが 1 となるイ ンピーダンス変換 器 1 6が得られる。  FIG. 3 shows a specific circuit example of the impedance converter 16 in the capacitance detection circuit 10 shown in FIG. FIG. 3A shows a voltage follower using the operational amplifier 100. Inversion of operational amplifier 100 The input terminal and the output terminal are short-circuited. By setting the non-inverting input terminal of the operational amplifier 100 as the input of the impedance converter 16 and the output terminal of the operational amplifier 100 as the output of the impedance converter 16, the input impedance is reduced. The impedance converter 16 is extremely high and has a voltage gain A of 1.
図 3 ( b ) は、 演算増幅器 1 0 1 を用いた非反転増幅回路を示してい る。 演算増幅器 1 0 1 の反転入力端子とグラン ド間に抵抗 ( R 10) 1 1 0が接続され、 演算増幅器 1 0 1 の反転入力端子と出力端子間にフィ一 ドバック抵抗 (抵抗 ( R 11) 3 3 ) が接続されている。 この演算増幅器 1 0 1 の非反転入力端子をイ ンピーダンス変換器 1 6の入力と し、 演算 増幅器 1 0 1 の出力端子をィ ンピーダンス変換器 1 6の出力とすること で、 入力イ ンピーダンスが極めて高く 、 電圧ゲイン Aが ( R 10+ R 11) ZR 10 となるィ ンピーダンス変換器 1 6が得られる。 図 3 ( c ) は、 図 3 ( a ) や図 3 ( b ) に示されるような演算増幅器 の入力段に C M O S構造のバッファを付加した回路を示している。 図示 されるように、 正負電源間に N型 M O S F E T 3 4 と P型 M O S F E T 3 5 とが抵抗 1 1 2、 1 1 3 を介して直列に接続され、 ノくッファの出力 が演算増幅器 1 0 0 (又は 1 0 1 ) の入力に接続されている。 このバッ ファの入力をイ ンピーダンス変換器 1 6の入力と し、 演算増幅器の出力 端子をイ ンピーダンス変換器 1 6の出力とすることで、 入力インピーダ ンスが極めて高いイ ンピーダンス変換器 1 6が得られる。 FIG. 3B shows a non-inverting amplifier circuit using the operational amplifier 101. A resistor (R10) 110 is connected between the inverting input terminal of the operational amplifier 101 and the ground, and a feedback resistor (resistance (R11)) is connected between the inverting input terminal and the output terminal of the operational amplifier 101. 3 3) is connected. By setting the non-inverting input terminal of the operational amplifier 101 as the input of the impedance converter 16 and the output terminal of the operational amplifier 101 as the output of the impedance converter 16, the input impedance is extremely low. As a result, an impedance converter 16 having a voltage gain A of (R10 + R11) ZR10 can be obtained. FIG. 3 (c) shows a circuit in which a buffer having a CMOS structure is added to the input stage of the operational amplifier as shown in FIGS. 3 (a) and 3 (b). As shown in the figure, an N-type MOSFET 34 and a P-type MOSFET 35 are connected in series between the positive and negative power supplies via resistors 112 and 113, and the output of the buffer is connected to the operational amplifier 100. (Or 101) input. By using the input of this buffer as the input of the impedance converter 16 and the output terminal of the operational amplifier as the output of the impedance converter 16, an impedance converter 16 with extremely high input impedance can be obtained. Can be
図 3 ( d ) は、 図 3 ( c ) の入力段のバッファのような回路を示して いる。 図示されるよ うに、 正負電源間に、 N型 M O S F E T 3 4 と P型 M O S F E T 3 5 とが直列に接続され、 両 M O S F E Tの接続部から出 力がなされる。  FIG. 3 (d) shows a circuit such as the buffer in the input stage of FIG. 3 (c). As shown in the figure, an N-type MOS FET 34 and a P-type MOS FET 35 are connected in series between the positive and negative power supplies, and an output is made from a connection between the two MOS FETs.
図 3 ( e ) は、 演算増幅器 1 0 2の非反転入力をイ ンピ一ダンス変換 器の入力と し、 演算増幅器 1 0 2の反転入力端子に抵抗 1 1 4の一端を 接続し、 演算増幅器 1 0 2の出力と反転入力間を抵抗 1 1 5を介して接 続したものとなっている。 図 3 ( d ) 及び図 3 ( e ) に示されるように、 こ う した構成をとることで入力イ ンピーダンスが極めて高いイ ンピ一ダ ンス変換器 1 6が得られる。  Figure 3 (e) shows the operational amplifier with the non-inverting input of the operational amplifier 102 as the input to the impedance converter, and connecting one end of a resistor 114 to the inverting input terminal of the operational amplifier 102. The output of 102 and the inverting input are connected via a resistor 115. As shown in FIGS. 3 (d) and 3 (e), by adopting such a configuration, an impedance converter 16 having an extremely high input impedance can be obtained.
(第 2の実施の形態)  (Second embodiment)
次に、 本発明の第 2の実施の形態における静電容量検出回路について 説明する。  Next, a capacitance detection circuit according to a second embodiment of the present invention will be described.
図 4は、 第 2の実施の形態例における静電容量検出回路 3 0の回路図 である。 この静電容量検出回路 3 0は、 大き〈分けて、 図 2に示された 静電容量検出回路 1 0に相当するコア部 3 1 、 そのコア部 3 1 の信号出 力端子 2 0での信号電圧 V01 を入力と して反転する反転部 3 2、 及び、 その反転部 3 2の出力端子 2 3での信号電圧 V 03 とコア部 3 1 の交流 出力端子 2 2での信号電圧 V 02 とを加算し、 出力端子 2 4に電圧 V04 の検出信号を出力する加算部 3 3から構成される。 FIG. 4 is a circuit diagram of the capacitance detection circuit 30 according to the second embodiment. This capacitance detection circuit 30 has a large size <a core section 31 corresponding to the capacitance detection circuit 10 shown in FIG. 2, and a signal output terminal 20 of the core section 31. Inverting section 32 that inverts with signal voltage V01 as input, and signal voltage V03 at output terminal 23 of inverting section 32 and alternating current of core section 31 It comprises an adder 33 that adds the signal voltage V 02 at the output terminal 22 and outputs a detection signal of the voltage V04 to the output terminal 24.
コア部 3 1 は、 図 2に示された静電容量検出回路 1 0 と同一の回路で ある。 したがって、 コア部 3 1 の信号出力端子 2 0の電圧 V01 は、 上記 式 5よ り、  The core unit 31 is the same circuit as the capacitance detection circuit 10 shown in FIG. Therefore, the voltage V01 of the signal output terminal 20 of the core unit 31 is given by the above equation 5,
V 01= - ( 1 + Cs Cf) ■ ( R2 R 1) · (Vin A) (式 6 ) となり、コア部 3 1 の交流出力端子 2 2の電圧 V 02は、上記式 1 よ り、 V 01 =-(1 + Cs Cf) ■ (R2 R 1) · (Vin A) (Equation 6), and the voltage V 02 of the AC output terminal 22 of the core 31 is calculated by the above equation 1.
V 02= - ( R 2/ R 1) - (V in/ A ) (式 7 ) V 02 =-(R 2 / R 1)-(V in / A) (Equation 7)
となる。  Becomes
反転部 3 2は、 可変抵抗 ( R 4) 4 0、 抵抗 ( R5) 4 1 、 可変抵抗 ( R 6) 4 2 、 コ ンデンサ 4 3及び演算増幅器 4 4 を備えた反転増幅回路で あり、 電圧利得が一 1 で、 かつ、 その出力端子 2 3での信号 V 03の位相 がコア部 3 1 の交流出力端子 2 2での信号 V 02 と同一になるように、可 変抵抗 ( R4) 4 0及び可変抵抗 ( R 6) 4 2の抵抗値が調整されている。 したがって、 この反転部 3 2の入力電圧 V 01 と出力電圧 V 03 とは、 理 想的には以下の関係が成り立つている。  The inverting section 32 is an inverting amplifier circuit including a variable resistor (R4) 40, a resistor (R5) 41, a variable resistor (R6) 42, a capacitor 43, and an operational amplifier 44. The variable resistor (R4) 4 is set so that the gain is 1 and the phase of the signal V03 at its output terminal 23 is the same as the signal V02 at the AC output terminal 22 of the core unit 31. The resistance values of 0 and the variable resistor (R6) 42 are adjusted. Therefore, the following relationship holds true between the input voltage V 01 and the output voltage V 03 of the inverting section 32.
V 03= - V 01 (式 8 )  V 03 =-V 01 (Equation 8)
加算部 3 3は、 抵抗値の等しい 3つの抵抗 ( R7) 4 5、 抵抗 ( R8) 4 6及び抵抗 ( R 9) 4 7が演算増幅器 4 8に接続された加算器である。 つまり、 2つの入力信号の電圧 V 02 及び V03 と、 出力電圧 V 04 とは、 以下の関係が成り立つ。  The adder 33 is an adder in which three resistors (R7) 45, resistors (R8) 46, and resistors (R9) 47 having the same resistance value are connected to the operational amplifier 48. That is, the following relationship is established between the voltages V 02 and V 03 of the two input signals and the output voltage V 04.
V 04= - ( V 02+ V 03) (式 9 )  V 04 =-(V 02+ V 03) (Equation 9)
この式 9に、 上記式 8 を代入して V03 を消去した後に、 上記式 6及び 式 7 を代入すると、  Substituting Equation 8 above into Equation 9 to eliminate V03, then substituting Equations 6 and 7 above,
V 04= V 01- V 02  V 04 = V 01- V 02
=一 ( C s/ C f) - ( R 2/ R 1) - ( V in/ A ) (式 1 0 ) が成り立つ。 つま り、 この静電容量検出回路 3 0の出力端子 2 4から 出力される検出信号の電圧 V04は、容量値 Csに比例することが分かる。 よって、 この電圧 V 04に基づいて、 種々の信号処理を施すことで、 未知 の容量値 C s又は容量変化を容易に特定することができる。 = 1 (Cs / Cf)-(R2 / R1)-(Vin / A) (Equation 10) Holds. In other words, it can be seen that the voltage V04 of the detection signal output from the output terminal 24 of the capacitance detection circuit 30 is proportional to the capacitance value Cs. Therefore, by performing various signal processing based on the voltage V04, an unknown capacitance value Cs or a change in capacitance can be easily specified.
この式 1 0 と第 1 の実施の形態例における検出信号の電圧 Vout を示 す式 5 とを比較して分かるように、 第 2の実施の形態例における静電容 量検出回路 3 0で得られる検出信号は、 第 1 の実施の形態例と異なり、 被検出コ ンデンサ 1 7の容量に比例する成分だけを含み、 不要なオフセ ッ ト分 (被検出コンデンサ 1 7に依存しない電圧) を含んでいない。 し たがって、 第 2の実施の形態例における検出信号から被検出コ ンデンサ 1 7の容量を特定する信号処理は、 簡易なもので済む。  As can be seen by comparing Expression 10 with Expression 5 indicating the voltage Vout of the detection signal in the first embodiment, the capacitance is obtained by the capacitance detection circuit 30 in the second embodiment. Unlike the first embodiment, the detection signal includes only a component proportional to the capacitance of the capacitor 17 to be detected, and includes an unnecessary offset (a voltage independent of the capacitor 17 to be detected). Not in. Therefore, the signal processing for specifying the capacitance of the capacitor 17 to be detected from the detection signal in the second embodiment is simple.
なお、 本例では、 V03=— V01 となる例で説明したが、 本発明は、 こ れに限定されるものではない。 容量センサの種類によ り、 V03= k · V 01 ( kは反転増幅部の増幅率) と して、 出力電圧 V 04が、  Note that, in the present embodiment, an example in which V03 = —V01 has been described, but the present invention is not limited to this. Depending on the type of the capacitance sensor, the output voltage V04 can be expressed as V03 = k · V01 (k is the gain of the inverting amplifier)
V 04= { k - ( C s/ C f) + ( k + 1 ) } ■ ( R 2/ R 1) ■ V in  V 04 = {k-(C s / C f) + (k + 1)} ■ (R 2 / R 1) ■ V in
となるように設定してもよい。  You may set so that it may become.
図 5は、 上記第 1 及び第 2の実施の形態例における静電容量検出回路 の電子機器への応用例を示す図である。 ここでは、 コ ンデンサマイク ロ ホンと静電容量検出回路とが一体化された、 携帯電話機等に用いられる マイク ロホン 5 0の断面図が示されている。 このマイク ロホン 5 0は、 音孔 5 2 を有する蓋体 5 1 と、 音によって振動する振動膜 5 3 と、 振動 膜 5 3 を固定しているリ ング 5 4 と、 スぺ一サ 5 5 a と、 スぺ一サ 5 5 a を介して振動膜 5 3 と対抗して設けられた固定電極 5 6 と、 固定電極 5 6を支持する絶縁板 5 5 b と、 絶縁板 5 5 bの裏面に固定された上記 施の形態の静電容量検出回路が形成された I Cチップ 5 8 と、 I Cチッ プ 5 8 をモール ドしている I Cノ《ッケージ 5 9 と、 I Cチップ 5 8 とヮ ィャボンディ ング等で接続された外部電極 6 1 a 、 6 1 b等とから構成 される。 FIG. 5 is a diagram showing an application example of the capacitance detection circuit in the first and second embodiments to an electronic device. Here, a cross-sectional view of a microphone 50 used for a mobile phone or the like in which a capacitor microphone and a capacitance detection circuit are integrated is shown. The microphone 50 includes a lid 51 having a sound hole 52, a vibrating membrane 53 vibrating by sound, a ring 54 fixing the vibrating membrane 53, and a speaker 55. a, a fixed electrode 56 provided opposite the vibrating membrane 53 via the spacer 55a, an insulating plate 55b supporting the fixed electrode 56, and an insulating plate 55b. The IC chip 58 fixed to the back surface and having the capacitance detection circuit of the above embodiment formed thereon, the IC package 59 molding the IC chip 58, the IC chip 58, and the like. It is composed of external electrodes 61a, 61b, etc. connected by bonding or the like.
コ ンデンサを形成している一方の電極である振動膜 5 3 は、 所定の電 位 (本例では、 接地) に接続され、 他方の電極である固定電極 5 6は、 アルミニウム板やワイヤボンディ ング、 コンタク トホール等の導電体を 介して I Cチップ 5 8の回路に接続されている。 振動膜 5 3 と固定電極 5 6 とからなるコ ンデンサの容量又はその変化は、 絶縁板 5 5 b を介し て隣接する I Cチップ 5 8内の静電容量検出回路によって検出され、 電 気信号に変換されて、外部電極 6 1 a . 6 1 b等から出力される。なお、 蓋体 5 1 は、 アルミニウム等の金属からなり、 絶縁基板 6 0の上面に形 成された導電膜 (図示せず) とともに、 内部のコンデンサ 5 3、 5 6や I Cチップ 5 8への外乱ノ イズの侵入を遮蔽するシール ドボックスと し ての役割を果たしている。 また本例では、 固定電極 5 6 と回路とを接続 し、 振動膜 5 3 を所定の電位に接続しているが、 振動膜 5 3 と回路とを 接続し、 固定電極 5 6 を所定の電位に接続してもよい。 ただし、 経験的 には前者の方が好ましい。  The vibrating membrane 53, which is one of the electrodes forming the capacitor, is connected to a predetermined potential (ground in this example), and the fixed electrode 56, which is the other electrode, is made of an aluminum plate or wire bonding. It is connected to the circuit of the IC chip 58 through a conductor such as a contact hole. The capacitance of the capacitor composed of the vibrating membrane 53 and the fixed electrode 56 or its change is detected by the capacitance detection circuit in the adjacent IC chip 58 via the insulating plate 55b, and is detected by the electric signal. It is converted and output from the external electrodes 6 1a. The lid 51 is made of a metal such as aluminum, and has a conductive film (not shown) formed on the upper surface of the insulating substrate 60 as well as the internal capacitors 53, 56 and the IC chip 58. It plays a role as a shield box that blocks intrusion of disturbance noise. In this example, the fixed electrode 56 and the circuit are connected to each other, and the vibrating membrane 53 is connected to a predetermined potential. However, the vibrating membrane 53 and the circuit are connected to each other, and the fixed electrode 56 is connected to the predetermined potential. May be connected. However, empirically, the former is preferred.
図 6は、 図 5に示されたマイク ロホン 5 0の概略的な外観図である。 図 6 ( a ) は平面図、 図 6 ( b ) は正面図、 図 6 ( c ) は底面図である。 図 6 ( a )、 ( b ) に示された蓋体 5 1 の大きさは、 例えば、 およそ ø縦 5 mm x高さ 2 mmである。 図 6 ( c ) に示された 4つの外部電極 6 1 a ~ 6 1 dは、 例えば、 静電容量検出回路の電源用の 2つの端子と、 出 力信号用の 2つの端子である。  FIG. 6 is a schematic external view of the microphone 50 shown in FIG. Fig. 6 (a) is a plan view, Fig. 6 (b) is a front view, and Fig. 6 (c) is a bottom view. The size of the lid 51 shown in FIGS. 6 (a) and 6 (b) is, for example, approximately 5 mm long and 2 mm high. The four external electrodes 61 a to 61 d shown in FIG. 6C are, for example, two terminals for the power supply of the capacitance detection circuit and two terminals for the output signal.
このような応用例においては、 被検出コンデンサ (ここでは、 コ ンデ ンサマイク ロホン) と静電容量検出回路 (ここでは、 I Cチップ) とは 隣接して設けられ、 信号線は極めて短く 、 その浮遊容量がコンデンサマ イク 口ホンか回路内の第 1 インピーダンス素子のいずれか大きい方の容 量値の 1 0倍を超えないよ うな長さの導電体によって接続されている。 そして、 それらの部品は、 金属製の蓋体等のシール ド部材で覆われてい る。 したがって、 このような応用例においては、 被検出コ ンデンサと静 電容量検出回路とを接続する信号線 (導電体) に混入する外乱ノ イズ等 の悪影響については無視することができると考えられる。 In such an application, the capacitor to be detected (here, a capacitor microphone) and the capacitance detection circuit (here, an IC chip) are provided adjacent to each other, and the signal line is extremely short. Capacitor microphone Capacitor microphone or first impedance element in circuit, whichever is greater It is connected by a conductor whose length does not exceed 10 times the quantity value. These components are covered with a shield member such as a metal lid. Therefore, in such an application example, it is considered that adverse effects such as disturbance noise mixed in the signal line (conductor) connecting the capacitor to be detected and the capacitance detection circuit can be ignored.
つま り、 このよ うな小型のマイク ロホンにおいては、 被検出コンデン サと静電容量検出回路とは極めて短い導電体で接続されるので、 その間 をシ一ル ド付きケーブルで接続したり、 そのシール ドにガー ド電圧を印 加するための特殊な回路を設けることは、却って、回路規模を大きく し、 回路のコ ンパク ト 匕を妨げる。 したがって、 被検出コ ンデンサと静電容 量検出回路とは、 非シール ドの (シール ドされていない) 導電板、 配線 パターン、 ワイヤボンディ ング、 リ一 ド線等によ り、 最短経路を接続す るのが好ましい。 他のマイク ロホンの例と して、 図 7及び図 8に、 回路 を基板にのせたものを示す。 上記実施の形態例の静電容量検出回路が基 板 6 2に搭載された以外は基本的に同じである。  In other words, in such a small microphone, the capacitor to be detected and the capacitance detection circuit are connected by an extremely short conductor. Providing a special circuit for applying a guard voltage to the gate rather increases the circuit scale and prevents the circuit from being compact. Therefore, the shortest path between the capacitor to be detected and the capacitance detection circuit should be connected by a non-shielded (unshielded) conductive plate, wiring pattern, wire bonding, lead wire, etc. Preferably. As examples of other microphones, Figs. 7 and 8 show the circuit mounted on a board. This is basically the same as the above embodiment except that the capacitance detection circuit is mounted on the substrate 62.
以上、 本発明に係る静電容量検出回路について、 2つの実施の形態例 及び製品への応用例に基づいて説明したが、 本発明は、 これらの実施の 形態例及び応用例に限定されるものではない。  As described above, the capacitance detection circuit according to the present invention has been described based on the two embodiments and the application to the product. However, the present invention is limited to these embodiments and the application. is not.
例えば、 静電容量検出回路 1 0及び 3 0において、 被検出コンデンサ 1 7 に流れる電流を検出するために、 演算増幅器 1 4 とイ ンピーダンス 変換器 1 6 との間に、 コ ンデンサ 1 5が接続されたが、 抵抗やイ ンダク タ ンス等のイ ンピーダンス素子を接続することも考慮可能である。 また、 図 9に示されるよ うに、 上記実施の形態における静電容量検出 回路 1 0及び 3 0におけるコンデンサ 1 5 と並列に抵抗 1 8を付加して 接続してもよい。 これによつて、 コ ンデンサ 1 5 と被検出コンデンサ 1 7 との接続点は、 抵抗 1 8 を介して第 1 演算増幅器 1 4の出力端子と接 続されることになリ 、 直流的にフローティ ング状態となることが解消さ れ、 電位が固定される。 For example, in the capacitance detection circuits 10 and 30, a capacitor 15 is connected between the operational amplifier 14 and the impedance converter 16 to detect the current flowing through the capacitor 17 to be detected. However, it is also possible to consider connecting an impedance element such as a resistor or an inductance. Further, as shown in FIG. 9, a resistor 18 may be added in parallel with the capacitor 15 in the capacitance detection circuits 10 and 30 in the above embodiment and connected. As a result, the connection point between the capacitor 15 and the capacitor 17 to be detected is connected to the output terminal of the first operational amplifier 14 via the resistor 18. As a result, the DC floating state is eliminated, and the potential is fixed.
また、 被検出コ ンデンサ 1 7 と して接続される容量型センサは、 コン デンサマイク ロホンだけに限られず、 加速度センサ、 地震計、 圧力セン サ、 変位センサ、 変位計、 近接センサ、 タ ツチセンサ、 イオンセンサ、 湿度センサ、 雨滴センサ、 雪センサ、 雷センサ、 位置合わせセンサ、 接 触不良センサ、 形状センサ、 終点検出センサ、 振動センサ、 超音波セン サ、 角速度センサ、 液量センサ、 ガスセンサ、 赤外線センサ、 放射線セ ンサ、 水位計、 凍結センサ、 水分計、 振動計、 帯電センサ、 プリ ン ト基 板検査機等の公知の容量型センサなど、 静電容量の変化を利用して各種 物理量を検出する全ての トランスデューサ (デバイス) が含まれる。 以上の説明から明らかなよ うに、 本発明に係る静電容量検出回路、 静 電容量検出装置及びマイク ロホン装置は、 抵抗を介して演算増幅器に交 流電圧を印加し、 信号線に被検出コ ンデンサを接続することで、 被検出 コンデンサの容量を検出 している。 つま り、 非反転入力端子を所定の電 位に接続した演算増幅器の出力端子とイ ンピーダンス変換器の入力端子 間にコ ンデンサを接続すると ともに、 イ ンピ一ダンス変換器の入力端子 と所定の電位間に被検出コ ンデンサを接続している。  In addition, the capacitive sensors connected as the detected capacitors 17 are not limited to capacitor microphones, but also include acceleration sensors, seismometers, pressure sensors, displacement sensors, displacement meters, proximity sensors, touch sensors, and ion sensors. Sensor, humidity sensor, raindrop sensor, snow sensor, lightning sensor, alignment sensor, poor contact sensor, shape sensor, end point detection sensor, vibration sensor, ultrasonic sensor, angular velocity sensor, liquid level sensor, gas sensor, infrared sensor, Radiation sensors, water level gauges, freeze sensors, moisture meters, vibrometers, charge sensors, well-known capacitive sensors such as printed circuit board inspection machines, etc., all of which detect various physical quantities using changes in capacitance Of transducers (devices). As is apparent from the above description, the capacitance detection circuit, the capacitance detection device, and the microphone device according to the present invention apply the AC voltage to the operational amplifier via the resistor, and apply the detected voltage to the signal line. The capacitance of the capacitor to be detected is detected by connecting a capacitor. That is, a capacitor is connected between the output terminal of the operational amplifier whose non-inverting input terminal is connected to the predetermined potential and the input terminal of the impedance converter, and the input terminal of the impedance converter is connected to the predetermined potential. The detected capacitor is connected between them.
これによつて、 被検出コ ンデンサに流れる電流の全てがコンデンサに 流れ、 演算増幅器の出力端子には被検出コンデンサの容量に対応する正 確な信号が出力されること となり、 数 p Fあるいは f Fオーダ一以下の 微小な容量の検出が可能となる。  As a result, all of the current flowing through the capacitor to be detected flows into the capacitor, and an accurate signal corresponding to the capacitance of the capacitor to be detected is output to the output terminal of the operational amplifier. It is possible to detect minute capacitances of F order or less.
そ して、 演算増幅器の非反転入力端子は所定の電位に接続され、 入力 端子の一方の電位が固定されるので、 演算増幅器は安定して動作し、 演 算誤差が低減し、 検出信号に含まれるノ イズが抑制される。  Then, the non-inverting input terminal of the operational amplifier is connected to a predetermined potential, and one potential of the input terminal is fixed, so that the operational amplifier operates stably, the operational error is reduced, and the detection signal is reduced. Included noise is suppressed.
また、 演算増幅器とィ ンピーダンス変換器との間にコ ンデンザが接続 されているので、演算増幅器に印加される交流電圧の周波数に依存せず、 被検出コンデンサの容量変化の周波数にも依存しない検出感度が確保さ れる。 さ らに、 演算増幅器とインピ一ダンス変換器との間に抵抗を接続 した場合におけるその抵抗からの熱雑音による S Z N比の劣化という問 題も生じない。 A capacitor is connected between the operational amplifier and the impedance converter. As a result, detection sensitivity is ensured that does not depend on the frequency of the AC voltage applied to the operational amplifier and does not depend on the frequency of the capacitance change of the capacitor to be detected. Furthermore, when a resistor is connected between the operational amplifier and the impedance converter, there is no problem of deterioration of the SZN ratio due to thermal noise from the resistor.
なお、 この静電容量検出回路と被検出コ ンデンサとを隣接した位置に 設けておく か、 又は、 信号線に接続される回路素子を近接して設けるこ とで、 この間を接続するシール ドケーブルや、 そのケーブルで発生する 浮遊容量をキャンセルする特殊な回路等は不要となる。  The capacitance detection circuit and the capacitor to be detected may be provided adjacent to each other, or a circuit element connected to the signal line may be provided close to the capacitance detection circuit, and a shielded cable may be connected between them. Also, there is no need for a special circuit to cancel the stray capacitance generated in the cable.
ここで、 前記静電容量検出回路に、 信号出力端子での信号を反転する 反転増幅回路と、 イ ンピーダンス変換器の出力信号と反転増幅回路の出 力信号とを加算する加算回路とを付加してもよい。 これによつて、 静電 容量検出回路の出力信号に含まれる不要なオフセッ ト成分が除去され、 被検出コ ンデンサの容量に対応する正味の信号を大き く 増幅することが できる。  Here, an inverting amplifier circuit for inverting the signal at the signal output terminal and an adding circuit for adding the output signal of the impedance converter and the output signal of the inverting amplifier circuit are added to the capacitance detecting circuit. You may. As a result, unnecessary offset components included in the output signal of the capacitance detection circuit are removed, and a net signal corresponding to the capacitance of the detected capacitor can be greatly amplified.
また、 被検出コンデンサをコンデンサマイク ロホンと し、 静電容量検 出回路については I Cで実現し、 それらコンデンサマイクホンと I Cと を一体化し、 携帯電話機等に使用されるマイク ロホンと して 1 つの筐体 (シール ドボックス) に収めることで、 コ ンデンサマイク ロホンと静電 容量検出回路とは極めて隣接した位置に配置されるので、 被検出コンデ ンサと静電容量検出回路とを接続するための径の大きなシール ドケープ ルゃガー ド電圧を印加するための特殊な回路等が不要となる。  The capacitor to be detected is a condenser microphone, and the capacitance detection circuit is realized by an IC. The condenser microphone and the IC are integrated into one microphone as a microphone used in mobile phones and the like. Since the capacitor microphone and the capacitance detection circuit are placed very close to each other by being housed in a housing (shield box), the capacitor to be detected and the capacitance detection circuit are connected to each other. A special circuit, etc. for applying a large-diameter shield cap lug guard voltage is not required.
さ らに、 本発明に係る静電容量検出回路は、 被検出コ ンデンサに電流 を流すことによって容量を検出しているので、 エレク ト レッ トコ ンデン サマイク ロホン等のよ うに、 被検出コンデンサの電極に高分子フィルム 等を貼り付けてエレク ト レッ ト化する必要がなく 、 通常の静電容量型セ ンサに適用することができる。 Further, since the capacitance detection circuit according to the present invention detects the capacitance by applying a current to the capacitor to be detected, the capacitance of the capacitor to be detected is, for example, an electret capacitor microphone. There is no need to attach a polymer film or the like to the Can be applied to sensors.
以上のように、 本発明によ り、 使用環境の限定も少なく なリ、 微小な 容量を正確に検出することができ、 かつ、 小型化に適した静電容量検出 回路等が実現され、 特に、 携帯電話機等の軽量 ' 小型の音声通信機器の 音声性能が飛躍的に向上され、 その実用的価値は極めて高い。 産業上の利用の可能性  As described above, according to the present invention, it is possible to accurately detect a small capacitance with a limited use environment and realize a capacitance detection circuit and the like suitable for miniaturization. The voice performance of lightweight and small voice communication devices such as mobile phones has been dramatically improved, and their practical value is extremely high. Industrial applicability
本発明に係る静電容量検出回路は、 容量型センサの検出回路と して、 特に、 携帯電話機等の小型 ' 軽量の機器に備えられるマイク ロホン装置 と して利用することができる。  INDUSTRIAL APPLICABILITY The capacitance detection circuit according to the present invention can be used as a detection circuit of a capacitive sensor, particularly as a microphone device provided in a small and lightweight device such as a mobile phone.

Claims

請 求 の 範 囲 The scope of the claims
1 . 被検出コ ンデンサの静電容量に対応する検出信号を出力する静 電容量検出回路であって、  1. A capacitance detection circuit that outputs a detection signal corresponding to the capacitance of a capacitor to be detected,
入力イ ンピーダンスが高く 出力イ ンピーダンスが低いイ ンピーダンス 変換器と、 容量性の第 1 インピーダンス素子と、 演算増幅器と、 前記演 算増幅器に交流電圧を印加する交流電圧発生器と、 前記演算増幅器の出 力に接続される信号出力端子とを備え、  An impedance converter having a high input impedance and a low output impedance, a capacitive first impedance element, an operational amplifier, an AC voltage generator for applying an AC voltage to the operational amplifier, and an output of the operational amplifier. A signal output terminal connected to the
前記イ ンピーダンス変換器の入力端子には前記被検出コ ンデンザの一 端と前記第 1 イ ンピーダンス素子の一端とが接続され、  One end of the detected capacitor and one end of the first impedance element are connected to an input terminal of the impedance converter,
前記演算増幅器の負帰還路に前記第 1 イ ンピーダンス素子及び前記ィ ンピ一ダンス変換器が含まれ、  A negative feedback path of the operational amplifier includes the first impedance element and the impedance converter;
前記被検出コ ンデンサと前記静電容量検出回路とは隣接して設けられ ている  The capacitor to be detected and the capacitance detection circuit are provided adjacent to each other.
ことを特徴とする静電容量検出回路。  A capacitance detection circuit characterized by the above-mentioned.
2 . 被検出コンデンサの静電容量に対応する検出信号を出力する静 電容量検出回路であって、 2. A capacitance detection circuit that outputs a detection signal corresponding to the capacitance of a capacitor to be detected,
入力イ ンピ一ダンスが高く 出力インピーダンスが低いインピーダンス 変換器と、 容量性の第 1 インピーダンス素子と、 演算増幅器と、 前記演 算増幅器に交流電圧を印加する交流電圧発生器と、 前記演算増幅器の出 力に接続される信号出力端子とを備え、  An impedance converter having a high input impedance and a low output impedance, a capacitive first impedance element, an operational amplifier, an AC voltage generator for applying an AC voltage to the operational amplifier, and an output of the operational amplifier. A signal output terminal connected to the
前記インピーダンス変換器の入力端子には前記被検出コンデンサの一 端と前記第 1 ィ ンピ一ダンス素子の一端とが接続され、  One end of the capacitor to be detected and one end of the first impedance element are connected to an input terminal of the impedance converter,
前記演算増幅器の負帰還路に前記第 1 イ ンピーダンス素子及び前記ィ ンピーダンス変換器が含まれ、  The first impedance element and the impedance converter are included in a negative feedback path of the operational amplifier;
前記被検出コ ンデンサと前記第 1 インピーダンス素子と前記イ ンピー ダンス変換器とが近接して設けられている The detected capacitor, the first impedance element, and the impedance Close to the dance converter
ことを特徴とする静電容量検出回路。  A capacitance detection circuit characterized by the above-mentioned.
3 . 前記静電容量検出回路は、 さ らに、 前記第 1 イ ンピーダンス素 子と並列に接続される抵抗素子を含む 3. The capacitance detection circuit further includes a resistance element connected in parallel with the first impedance element.
ことを特徴とする請求の範囲 1 又は 2記載の静電容量検出回路。  The capacitance detection circuit according to claim 1 or 2, wherein:
4 . 前記交流電圧発生器と前記演算増幅器との間に設けられた第 2 インピーダンスをさ らに備えた 4. A second impedance provided between the AC voltage generator and the operational amplifier is further provided.
ことを特徴とする請求の範囲 1 〜 3のいずれか 1 項に記載の静電容量 検出回路。  The capacitance detection circuit according to any one of claims 1 to 3, wherein:
5 . 前記静電容量検出回路は、 さ らに、 5. The capacitance detection circuit further comprises:
前記信号出力端子での信号を反転する反転増幅回路と、  An inverting amplifier circuit for inverting a signal at the signal output terminal;
前記イ ンピ一ダンス変換器の出力信号と前記反転増幅回路の出力信号 とを加算する加算回路とを備える  An adder circuit for adding an output signal of the impedance converter and an output signal of the inverting amplifier circuit;
ことを特徴とする請求の範囲 1 ~ 4のいずれか 1 項に記載の静電容量 検出回路。  The capacitance detection circuit according to any one of claims 1 to 4, characterized in that:
6 . 前記被検出コンデンサの一端と前記イ ンピーダンス変換器の入 力端子とは非シール ドの導電体で接続される 6. One end of the capacitor to be detected and the input terminal of the impedance converter are connected by a non-shielded conductor.
ことを特徴とする請求の範囲 1 〜 5のいずれか 1 項に記載の静電容量 検出回路。  The capacitance detection circuit according to any one of claims 1 to 5, wherein:
7 . 前記被検出コンデンサ及び前記静電容量検出回路は、 1 つのシ 一ル ドボックス内に収納されている ことを特徴とする請求の範囲 1 〜 6のいずれか 1 項に記載の静電容量 検出回路。 7. The capacitor to be detected and the capacitance detection circuit are housed in one shield box The capacitance detection circuit according to any one of claims 1 to 6, wherein:
8 . 容量の変化に応じて物理量を検出する前記被検出コンデンサと して容量型センサと、 8. A capacitive sensor as the detected capacitor for detecting a physical quantity according to a change in capacitance;
プリ ン ト基板又はシリ コ ン基板上に形成され、 前記容量型センサに固 定して設けられている請求の範囲 1 〜 7のいずれか 1 項に記載の静電容 量検出回路と  The capacitance detection circuit according to any one of claims 1 to 7, wherein the capacitance detection circuit is formed on a print substrate or a silicon substrate, and is fixed to the capacitive sensor.
を備えることを特徴とする静電容量検出装置。  A capacitance detection device comprising:
9 . 前記被検出コンデンサと してのコ ンデンサマイク ロホンと、 請求の範囲 1 ~ 7のいずれか 1 項に記載の静電容量検出回路と を備えること を特徴とするマイク ロホン装置。 9. A microphone device comprising: a capacitor microphone as the capacitor to be detected; and the capacitance detection circuit according to any one of claims 1 to 7.
PCT/JP2002/009138 2001-09-06 2002-09-06 Capacitance measuring circuit, capacitance measuring instrument, and microphone device WO2003023421A1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US10/488,763 US7019540B2 (en) 2001-09-06 2002-09-06 Electrostatic capacitance detection circuit and microphone device
KR1020047003329A KR100715062B1 (en) 2001-09-06 2002-09-06 Capacitance measuring circuit, capacitance measuring instrument, and microphone device
EP02767922A EP1426773A4 (en) 2001-09-06 2002-09-06 Capacitance measuring circuit, capacitance measuring instrument, and microphone device
NO20032012A NO20032012L (en) 2001-09-06 2003-05-05 Electrostatic capacitance detection circuit, electrostatic capacitance detection device and microphone device

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2001-269993 2001-09-06
JP2001269993 2001-09-06

Publications (1)

Publication Number Publication Date
WO2003023421A1 true WO2003023421A1 (en) 2003-03-20

Family

ID=19095712

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2002/009138 WO2003023421A1 (en) 2001-09-06 2002-09-06 Capacitance measuring circuit, capacitance measuring instrument, and microphone device

Country Status (7)

Country Link
US (1) US7019540B2 (en)
EP (1) EP1426773A4 (en)
KR (1) KR100715062B1 (en)
CN (1) CN1271418C (en)
NO (1) NO20032012L (en)
TW (1) TWI221195B (en)
WO (1) WO2003023421A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111238098A (en) * 2018-11-29 2020-06-05 桂林航天工业学院 Real-time monitoring system for air conditioner heat exchanger

Families Citing this family (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7663607B2 (en) 2004-05-06 2010-02-16 Apple Inc. Multipoint touchscreen
JP4310234B2 (en) * 2004-05-18 2009-08-05 株式会社オーディオテクニカ Condenser microphone
TW200614846A (en) * 2004-09-24 2006-05-01 Hosiden Corp Signal amplifying circuit and acceleration sensor having the same
US8552989B2 (en) * 2006-06-09 2013-10-08 Apple Inc. Integrated display and touch screen
CN104965621B (en) 2006-06-09 2018-06-12 苹果公司 Touch screen LCD and its operating method
KR102481798B1 (en) 2006-06-09 2022-12-26 애플 인크. Touch screen liquid crystal display
JP2008135147A (en) * 2006-10-24 2008-06-12 D & M Holdings Inc Operating element and reproducer
US8493330B2 (en) * 2007-01-03 2013-07-23 Apple Inc. Individual channel phase delay scheme
US9710095B2 (en) 2007-01-05 2017-07-18 Apple Inc. Touch screen stack-ups
DE102008035627A1 (en) * 2008-07-31 2010-02-11 Gerd Reime Device for the capacitive measurement of changes
KR101471801B1 (en) * 2009-08-21 2014-12-10 애플 인크. Methods and apparatus for capacitive sensing
US20110273189A1 (en) * 2010-05-06 2011-11-10 Steve Gerber Sensing apparatus for and associated methods
US8804056B2 (en) * 2010-12-22 2014-08-12 Apple Inc. Integrated touch screens
DE102011083052B4 (en) * 2011-09-20 2016-03-10 Hauni Maschinenbau Ag Capacitive HF strand measuring device and stranding machine
GB2550402B (en) 2016-05-19 2022-04-20 Ultra Electronics Ltd Circuit for simulating a capacitance fuel probe
FR3072176B1 (en) * 2017-10-10 2022-03-04 Fogale Nanotech IMPEDANCE MEASUREMENT DEVICE
JP7132015B2 (en) * 2018-07-24 2022-09-06 アズビル株式会社 electrical conductivity meter
CN110061710A (en) * 2019-05-30 2019-07-26 杭州欧贲科技有限公司 Highly integrated charge amplifier circuit
CN113008275A (en) * 2021-03-01 2021-06-22 上海木西电子科技有限公司 Capacitive analog quantity signal output sensor

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09280806A (en) * 1996-04-09 1997-10-31 Nissan Motor Co Ltd Electrostatic capacitance type displacement meter
WO1999038019A1 (en) * 1998-01-23 1999-07-29 Sumitomo Metal Industries, Ltd. Static capacitance-to-voltage converter and converting method
JP2001324520A (en) * 2000-03-07 2001-11-22 Sumitomo Metal Ind Ltd Impedance detection circuit, impedance detection device, and impedance detection method
JP2002022785A (en) * 2000-07-10 2002-01-23 Sumitomo Metal Ind Ltd Impedance detecting circuit and impedance detecting method
JP2002022786A (en) * 2000-07-10 2002-01-23 Sumitomo Metal Ind Ltd Impedance detecting circuit and impedance detecting method
JP2002157671A (en) * 2000-11-16 2002-05-31 Sumitomo Metal Ind Ltd Sensing system

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4918376A (en) * 1989-03-07 1990-04-17 Ade Corporation A.C. capacitive gauging system
TW418323B (en) * 1998-02-19 2001-01-11 Sumitomo Metal Ind Capacitance detection system and method
JP4124867B2 (en) * 1998-07-14 2008-07-23 松下電器産業株式会社 Conversion device

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09280806A (en) * 1996-04-09 1997-10-31 Nissan Motor Co Ltd Electrostatic capacitance type displacement meter
WO1999038019A1 (en) * 1998-01-23 1999-07-29 Sumitomo Metal Industries, Ltd. Static capacitance-to-voltage converter and converting method
JP2001324520A (en) * 2000-03-07 2001-11-22 Sumitomo Metal Ind Ltd Impedance detection circuit, impedance detection device, and impedance detection method
JP2002022785A (en) * 2000-07-10 2002-01-23 Sumitomo Metal Ind Ltd Impedance detecting circuit and impedance detecting method
JP2002022786A (en) * 2000-07-10 2002-01-23 Sumitomo Metal Ind Ltd Impedance detecting circuit and impedance detecting method
JP2002157671A (en) * 2000-11-16 2002-05-31 Sumitomo Metal Ind Ltd Sensing system

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP1426773A4 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111238098A (en) * 2018-11-29 2020-06-05 桂林航天工业学院 Real-time monitoring system for air conditioner heat exchanger

Also Published As

Publication number Publication date
CN1271418C (en) 2006-08-23
KR20040041603A (en) 2004-05-17
TWI221195B (en) 2004-09-21
NO20032012L (en) 2003-07-03
CN1551990A (en) 2004-12-01
KR100715062B1 (en) 2007-05-04
US20050017737A1 (en) 2005-01-27
EP1426773A4 (en) 2005-09-21
EP1426773A1 (en) 2004-06-09
NO20032012D0 (en) 2003-05-05
US7019540B2 (en) 2006-03-28

Similar Documents

Publication Publication Date Title
WO2003023421A1 (en) Capacitance measuring circuit, capacitance measuring instrument, and microphone device
TWI221196B (en) Impedance measuring circuit, its method, and electrostatic capacitance measuring circuit
KR100715063B1 (en) Capacitance measuring circuit, capacitance measuring instrument, and microphone device
US20120076322A1 (en) Microphone
JP4072400B2 (en) Capacitance detection circuit, capacitance detection device, and microphone device
WO2003023419A1 (en) Impedance measuring circuit and capacitance measuring circuit
WO2003023417A1 (en) Sensor capacity sensing apparatus and sensor capacity sensing method
JP2003075487A (en) Impedance detection apparatus and capacitance detection apparatus
JP4071581B2 (en) Capacitance detection circuit, capacitance detection device, and microphone device
JP4071582B2 (en) Impedance detection circuit and method thereof
JP2003075481A (en) Impedance detection circuit and capacitance detection circuit
JP4072401B2 (en) Impedance detection circuit and capacitance detection circuit
JP2003075486A (en) Impedance detection circuit, and capacitance detection circuit and method
JP4282321B2 (en) Impedance detection device and impedance detection method
JP2004007481A (en) Electrostatic capacitance detecting circuit and detecting method
JP2002044777A (en) Microphone device
JP2003075484A (en) Capacitance detection circuit and method

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BY BZ CA CH CN CO CR CU CZ DE DM DZ EC EE ES FI GB GD GE GH HR HU ID IL IN IS KE KG KP KR KZ LK LR LS LT LU LV MA MD MG MK MW MX MZ NO NZ OM PH PL PT RO SD SE SG SI SK SL TJ TM TN TR TT UA UG US UZ VC VN YU ZA ZM

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH GM KE LS MW MZ SD SL SZ UG ZM ZW AM AZ BY KG KZ RU TJ TM AT BE BG CH CY CZ DK EE ES FI FR GB GR IE IT LU MC PT SE SK TR BF BJ CF CG CI GA GN GQ GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
WWE Wipo information: entry into national phase

Ref document number: 2002767922

Country of ref document: EP

WWE Wipo information: entry into national phase

Ref document number: 20028174011

Country of ref document: CN

Ref document number: 1020047003329

Country of ref document: KR

WWP Wipo information: published in national office

Ref document number: 2002767922

Country of ref document: EP

WWE Wipo information: entry into national phase

Ref document number: 10488763

Country of ref document: US